Guide to Fish Compatibility

Fish compatibility is the most difficult subject in the industry, and the greatest topic of controversy among professional aquarists. Those of us at the Aquarium Professionals Group with many years of experience are still learning about the subject. The problem is that there are no definite right or wrong answers when it comes to deciding which fish we can keep together in an aquarium. Some cases are obvious . . . or are they? No professional aquarist in their right mind would recommend keeping huge freshwater Oscars with tiny Neon Tetras. Yet the fact remains that our most experienced aquarists have seen the most improbable combinations of fish kept together without any compatibility problems. So as we began drawing up the first draft of our articles for this up-date, the question was raised: Why bother discussing an aquarium issue that is so conceptual that there are no definite facts that can be related to the reader?

The answer to that question is simple, although the execution is not so easy. There are far too many unknowledgeable and/or unscrupulous pet and aquarium stores out there that don't know or may not care when they sell you incompatible fish. They want your money, and most do not offer adequate guarantees that cover for example, one fish eating another. We therefore felt we should at least provide some basic guidelines and tips to help ensure compatibility. These generalities should be used as a tentative guide, keeping in mind that when it comes to fish compatibility, nothing is written in stone!

(joke),When shopping for a fish that you're unfamiliar with, ask a lot of questions. Take the time to look the fish up in an aquarium reference book.

If you're shopping in a new store, make friends with the staff and owners. They may develop a case of "conscience" before selling you a fish that's incompatible with your aquarium or another specimen you want to buy.

Check the livestock guarantees of the store you're shopping in. If they only have a 24 hour guarantee, or no guarantee (common these days with saltwater fish), they may have no incentive to guide you carefully when it comes to compatibility. If the fish you buy causes trouble but doesn't die, they may not take it back for credit.

As a general rule for all saltwater aquariums, and most freshwater tanks, new fish should always be added in groups of two or more. This helps to spread out the aggression in the tank. An aggressive fish that's already in the tank cannot chase two or more newcomers at once. This gives the new fish an occasional break in the action and allows them some recovery time.

It is important not to confuse aggression with hunger or feeding habits. Just because a fish has a large mouth or eats whole fish in the wild, does not necessarily make it aggressive. Piranha are actually quite peaceful. So are most Moray Eels. African Cichlids are primarily herbivores (vegetarian), but are extremely aggressive. Even us so-called "experts" have a tendency to get a little anthropomorphic about our fish, by attributing human characteristics to our finned little buddies (see . . . there I go!). Fish behave almost entirely through instinct. An instinct to strike out at a tank mate that's invading a territory is not "acting mean". It’s simply an instinctual response to an external stimulus. That isn't to say that fish can't "learn". Anyone who's ever seen their fish splash water in the tank in order to get fed would disagree. In most cases though, what we perceive as mean or cowardly behavior, is simply instinctual behavior that is genetically programmed. The fish was literally born to follow these behavior patterns. Unlike dogs and cats, there is no proven way to modify instinctual behavior in fish.

Nearly all saltwater fish, with few exceptions (such as seahorses), are aggressive to some degree. They come from a hostile environment, and behave accordingly.

All aquariums have a pecking order among their inhabitants. There will always be an "Alpha" specimen at the top of the order, and a series of less aggressive "Beta" specimens all the way down to the bottom of the pecking order. If you remove the most aggressive fish from an aquarium, another will take its place at the top of the pecking order. Generally, as long as no actual bodily damage is occurring, it's best to leave well enough alone. Even an occasional nipped fin is no real cause for alarm (Missing fins are another story).

Nearly 99.99 % of all saltwater aquarium invertebrates do not belong in a marine fish-only aquarium. Invertebrates are the natural foods of the fish. The one good exception are hermit crabs, which are somewhat protected by the seashells they carry. You can experiment with anemones, and maybe a lobster or shrimp, as long as you understand that it's an experiment, with a possible disastrous (and expensive) outcome.

As a general rule for both freshwater and marine fish, if you want to combine several specimens together that you're unsure of in terms of compatibility, use the following plan of action:

1. Determine the relative aggressiveness of each specimen you want to put together on a scale of one to ten by reading up on each and asking questions.
2. Buy the two most peaceful fish FIRST, and get the largest specimens you can find.
3. Each set of fish that follows should be a little more aggressive than the first, and smaller than the last set you added.
4. The last fish that you add should be the most aggressive, but also the smallest of the desired group.
5. Synopsis: Add the least aggressive fish first and make sure it will be the biggest fish in the tank. Add fish in order of increased aggressive behavior with each fish being smaller than the last. The most aggressive fish is added last, and should be the smallest specimen in the tank. Using this method allows the more peaceful fish to set up their territories first. By making the more peaceful fish larger, you give them a fighting advantage over the more aggressive species.

When considering the purchase of larger, more aggressive, or very active fish, beware of any definite statements made by salespeople that the specimen will be compatible. Statements like "Oh that will definitely work.", as opposed to "It should work." deserve a second opinion. If you're in doubt, they should be too.

Unfortunately, it is all too common to see incompatibility in action in the tanks at a pet or aquarium retail store. We've seen plenty of cases where every fish in a pet store tank is hiding except one, who's calmly cruising the tank looking for trouble. This can be of educational benefit though, in that one can learn first-hand about certain species that don’t get along with one another.

As a very loose general rule, with many exceptions, fish that are extremely hyper-active may stress fish that are extremely peaceful and slow-moving. Use caution, and watch how the other fish in the tank react to the fast-moving specimen.

If a fish is alone in an aquarium, find out why it's by itself before you buy it, even if it looks like a great specimen. It very well might be in "jail" for a serious felony or two.

Seahorses are rarely compatible with other saltwater fish. Freshwater Bettas (Siamese Fighting Fish) are never compatible with each other, and are rarely compatible with other long-finned fish or very fast-moving fish. Discus (freshwater) are extremely difficult to keep, and will rarely work in a community tank. Killifish (freshwater) should be kept by themselves in a small tank, and are not usually compatible in a community tank.

Fish with large mouths relative to the rest of their body usually EAT OTHER FISH! A Frogfish, Angler, Toadfish, or Stonefish may be cute in a homely sort of way, but they can swallow another fish nearly two and a half times their size! If you have small fish, some other fish to look out for in saltwater are: Groupers, Lionfish, Snappers, Jacks, large Triggers, Trumpetfish, and large Wrasses. Some of the fish to be cautious of, if you have a peaceful freshwater community tank, are: Scats, Pacus, all large Cichlids, Gars, Arowanas, Tinfoil Barbs, Bala Sharks, African Cichlids, and even Silver Dollars. Remember that even if the fish is a small baby specimen, it’s going to grow up!

If all the fish are crowded together on one side of the tank, and one fish is at the other end of the tank, that lone fish is probably aggressive!

Another sign that there’s an aggressive fish in a tank is if one or more fish are lying on their sides or nose-up at the surface of the water. This is a submissive posture. Watch the tank for a while and eventually, you’ll see the "culprit" go up and nip at the fish that are submitting. PLEASE NOTE: The reverse could also be true in this case. The store may have put one or two specimens in the tank that are too peaceful to fit into that particular community.

(We hesitated to include this) Taxonomy is the classification of organisms in an ordered system that indicates natural relationships. Fish (as well as all other living things) are classified by comparing their anatomical, physiological and behavioral differences. The more similarities there are between two species, the more closely-related they are considered to be to one another. Animals are classified in the following order: Kingdom, Phylum, Class, Order, Family, Genus and Species. For example: Humans are classified as follows: Kingdom-Animalia (Metazoans), Phylum-Chordata, Class-Mammalia, Order-Primates, Family-Hominidae, Genus-Homo, Species-sapiens. Our "specific name" is Homo sapiens. Our common name is "Human". Taxonomy can apply to fish compatibility when you are considering purchasing two different fish that are closely-related (in the same Family or Genus). They might not get along if they are very similar in shape, color, feeding habits or behavioral patterns. This is truer in saltwater, where fish that belong to the same Genus will often not get along. In freshwater, larger, more aggressive fish that are also closely related may not be compatible with one another. We are in no way stating that any two closely-related fish are incompatible. In freshwater aquaria for example, most of the smaller, peaceful-community fish should be kept in groups or pairs. We are only saying that if you have a marine tank, or a freshwater tank with larger fish, caution should be exercised when considering a purchase of fish that belong to the same Family or Genus as a fish you already own, or another you’ve considered buying. If in doubt, give us a call.

Other factors to consider when buying two fish of the same Family or Genus, are:

The size of your tank (The bigger the tank, the more space there is for territories) The amount of decorations you have in your tank (Are there enough caves and hiding places? Sometimes buying more decorations with a new fish helps to establish new territories.) Do the fish come from the same geographical location? (If the answer is yes, they are less likely to get along.) Do the fish have very similar body shapes, coloration, or markings? (Even fish that are not closely-related may not be compatible if they look similar to one another.).

In most cases except one definite exception, two saltwater fish of the same species may not be kept together. Exceptions to this are some smaller, relatively peaceful marine fish such as Percula Clowns, Skunk Clowns (but not most other Clownfish), most Gobies, Blennies, some Damsels, and a few others. In some cases, marine fish of the same species may be kept in groups of three or more, but never in pairs. Exception: Two marine fish of the same species that were captured together in the ocean, and are being sold as a "pair" are always compatible if they’re in the same tank together at the store.

In freshwater, be careful buying mated pairs of Cichlids, Angelfish, large Gouramis, or any other fish if you have a peaceful community tank. Depending on the species, breeding pairs of fish, even smaller specimens, can get aggressive when it’s time to breed. By the way, occasionally there are "mated pairs" of saltwater fish offered for sale. If you love the fish and they’re healthy, by all means, buy them. Just don’t expect them to breed in captivity. The odds against them actually producing are greater than your odds of winning the lottery.

If you’re replacing a fish that died with another of the same species, always remember that two fish of the same species may not exhibit the same behavior. If you had a peaceful Humu Trigger, the next one may turn out to be "mean". If the last Blue Tang you had was aggressive, the next one you buy may be a "wimp". Just when a supposed "expert" claims that a certain fish is peaceful, someone comes along with a story about the same fish that became a holy terror in their tank!

If you have live plants in a freshwater tank, always ask if the fish you want eats plants.

If you have a freshwater tank, beware of buying brackish water fish for your aquarium. Brackish water fish are species that inhabit delta, marsh, coastal estuary and saltwater wetland ecosystems, where rivers feed into the ocean. These fish live in water that is slightly salty. Although they can survive for a while in 100% freshwater or saltwater, they will eventually die or do poorly if they do not get a fair amount (but not too much) salt in their water. This level of salt is too high for most freshwater fish, and too low for saltwater. Almost all aquarium and pet stores keep a wide variety of brackish specimens in their freshwater aquariums. Unfortunately, many of these stores will rarely inform you of the special requirements of these fish. They are: Archerfish, Scats, Monos, Anableps, all Gobies, Mudskippers, Walking Catfish, most Puffers (with only two true freshwater exceptions), most Mollies, Silver Sharks (a catfish species), Half beaks, Psychedelic Eels, Reed Eels, Bamboo Eels, and nearly all Pipefish (There is a true FW Pipefish, but it’s extremely rare).

Some Rough Fishes

That cute little fish you bought could turn into your biggest headache if you don't think before you purchase, so here are a few words to help you in your selection when considering buying that little cutie. Also here we will be talking about which fish will live with others in harmony. although even after careful selection, we sometimes get a small fish that will bully others a great deal bigger than themselves, but luckily this mainly happens at breeding time.

Any fish can become a rogue, it doesn't necessarily have to be a big fish, as even some small species of fish can become quite dominating at times, especially at breeding time.

Generally when we speak of rogues people tend to think of the bigger species like some of the Cichlids,

and many of this group do get to a stage where they will only tolerate fish either the same size, or bigger than themselves. Other types of rogues are the ones that will uproot everything you plant, move vast amounts of gravel that leaves your tank like a moonscape, and even move small rocks if they are in their way. Others will ram the heater against the tank side, or pull the uprights from the undergravel filters, and on occasions decide to knock the lid off the tank and try their hand at jumping from the tank and onto the floor. Many of the big Cichlids will attack your hand if you try to clean the tank or move something that will alter their environment, while others will practically roll over and let you scratch their belly. Just by the last sentence we can see that not all Cichlids are the same, so we can't brand any fish as being a rogue.

So what causes a fish to be aggressive? Several things can cause this, many of which we can do our best to avoid. Fish near or actually spawning, or looking after young should never be trusted with other fish if the are of an appreciable size. At this time adult fish become very possessive about territory and the safety of their young, so now is one time you should leave well alone and let the fish get on with what they were born to do. In some situations we may have to remove either one or both the parents, but Cichlids in general tend to take care of their young right up to the time they are ready to spawn again, and it has been known for them to care for two broods of fry only weeks apart. Many of the Mouthbrooders also do this and can have more than one brood all trying to retreat into the mother's mouth. Great stuff.

Many Cichlids are very selective about their partner, and many once mated, will remain with that same partner to the end. If one dies, then it is sometimes hard to get the remaining fish to accept a new mate, and I have found this to happen with the Angels, the Jewel Cichlids, and the Firemouths, but again, not all fish are the same, but in general Cichlids seem to create a very strong bond with the partner they choose. In more than one instance I have had the remaining fish die within a short while after losing its partner.

Rogue fish are generally territorial fish and will set up an invisible area that they call theirs and will not allow outsiders to move into their area. Not much can be done here, but re-arranging the tank sometimes helps by confusing the fish as to where his territory starts and ends.

If the fish in question is causing harm to the more docile occupants of the tank, then your only option is to either move the aggressor, or move the peaceful fish. One should really consider a spare tank for these situations, and when not in general use it can be used as a quarantine tank, or for holding newborn fry, but it should always be setup correctly at the right temperature and ready for any emergency.

Even the common Zebra Danio can become aggressive if others in the tank are smaller or not quite as quick as it is. Keeping just one of these fish tends to cause this problem, especially if the Zebra has grown to an appreciable size.

Take the little Dwarf Gourami. A wonderful colourful fish that is usually quite docile, but catch him at breeding time and it's a different story. This little fellow can be a real terror if he is guarding the nest and will send most fish twice his size running in fear to the other end of the tank. This will happen with most of the Gourami species, and the Bettas.

So what can you do to stop it? If you have a fish that bullies others you could try to find something to distract it. Many fish that bully are single species in a tank, like a lone Oscar or Angel. You could try getting another to take its attention away, and this works in many cases.

For the fish that are getting bullied, try additional planting, more places for them to hide in the way of rock arrangements with hiding places that the bullying fish can't get into. As a last resort your LFS (Local Fish Store) might take the large fish in trade for some smaller ones that would be less problematic.

You should not confuse breeding actions with bullying, as most fish tend to look and act aggressive at breeding time. In the case of the Livebearers the males will constantly harass the females, at times leaving the female quite exhausted. Nothing much can be done here as this is nature's way, but if the females become stressed at all you could try separating them from the males for a while, preferably till they have given birth. Returning to the Cichlids for a moment. Many of these species will lock jaws and seem as if they are going to rip each other apart, and this can become quite scary at times, and others will chase their mate around the tank as if they were going to kill it, but in many cases it is just a normal breeding pattern.

Fishes,NOT for the Beginner

There are some fish that the beginning aquarist should avoid. Then there are still others are others that do quite well in a beginner’s tank. And there are even some fish that get along quite well in the "beginner tank".

What is the difference between a "beginner tank" and a beginner’s tank? A beginner’s tank is simply one owned by a beginner. But the term "beginner tank" also implies a certain stigma…for better or worse it is set up in the typical way that beginners set up their first tank. The typical way a beginner, in Calgary in the year 2000, sets up a tank is this: the tank is about 40-liters in capacity, has an undergravel filter, a semi-submersible heater, an inexpensive single tube (or incandescent bulb) light/hood, a small power filter, and plastic plants. It is usually stocked with a few live bearers, a few tetras or barbs, and a single Corydoras catfish.

However, it is not necessary for a beginner to start out that way. It is possible (however unlikely) that the beginner was introduced to the hobby by an advanced aquarist who introduced him to living plants at the same time. Such a beginner could set up a fairly advanced looking tank the very first time out…complete with living plants and the more comfortable surroundings, more stable water conditions, and increased oxygen supply that plants give to fish.

But both planted and unplanted tanks are likely to suffer from the same beginner’s mistakes: over feeding, under feeding, over crowding; incompatible species mixes, insufficient climatization, temperature fluctuations, and intermittent neglect. It’s just that the consequences of this aren’t as bad if the tank has plants in it.

So what fish are good beginner’s fish? Actually, most of them, so a better question would be "what fish aren’t". And an even better question would be "which fish, among those fish a beginner is likely to buy, aren’t". A stingray is not a good beginner’s fish, but at $140 a pop a beginner isn’t likely to buy one anyway. However, there are several fishes that are commonly sold to beginners that in my opinion should not be.

First of these is the fancy guppy. On the face of it, the guppy should be a perfect beginner’s fish: easy to breed, small, active, non-aggressive. And wild type guppies are. But fancy guppies are very often so inbred that their genetic strength is pretty much down the toilet. Fancy guppies have very short reproductive lives (often being "old" by nine months of age), they swim only with labor, and have lowered fecundity. They also are prone to "death without known causes". But wild-type guppies are often no better, as the ones available nowadays are relegated to the "feeder" tank, sold for 10¢ a piece, and subject to neglect. So if the wild-type guppies are likely to be neglected, and the fancy guppies are likely to be genetic trash, should the beginner still have guppies? Yes, but I would definitely not buy them from a pet store… go to a guppy breeder. Another option is buy "Endler’s livebearers". These look a lot like guppies, but they are almost certainly a separate species. They are endangered in the wild and being maintained in the aquarium as a genetically sound fish. And of course they tend to be very well cared for.

Another fish for the beginner to avoid is the molly, of all types. Many domestic strains suffer from the same genetic defects as fancy guppies (there is even a misshapen "balloon" molly available, shudder). And wild mollies are surprisingly expensive. Also quite surprising is that mollies are quite sensitive to changes in temperature… surprising since they live quite happily in central Florida where winter temperatures can easily drop below 15C. And mollies like some salt in the water, which is often not good for their tank mates. It is best to leave mollies to the advanced hobbyist willing to provide them with their own quarters.

Swordtails might not be such a great idea either. A much better idea than mollies, perhaps, but I would still only recommend them with some trepidation. There are several types of high-fin swordtails available that are simply genetic garbage. These fish are even unable to breed at all without artificial insemination. But even setting aside these inbred-to-oblivion fish (which I can’t imagine anybody wanting), the typical swordtail can be a fairly aggressive fish. This doesn’t seem to get mentioned much, but swordtails can be very bossy. They really need more elbow room than the typical beginner’s tank will likely provide.

Another fish that I would not recommend to the beginner is the neon tetra. Neon tetras were historically considered to be very difficult fish. Most certainly not for the beginner. But then Southeast Asian fish breeders learned the secrets of neon breeding and started mass-producing an aquarium-strain neon. They bred a fish that looked like the wild neon but was much more adaptable to the aquarium environment. The result was a fish that was inexpensive, colorful, peaceful, and hardy – the perfect beginner’s fish. So why don’t I recommend them? Well, neons don’t seem to be very hardy anymore. I am not sure why. Maybe its because their price has dropped so low that they are no longer given adequate treatment during shipping ("who cares if they die, it would be cheaper to just order another batch than package these properly"). Or maybe the aquarium neon has now become so inbred that it’s suffering from its own genetic deficiencies. Maybe they are selling poisoned fish so that the customer will come back and buy more. I don’t know. But I do know that a lot of neons seem to die within a week of being purchased.

Another fish often sold to the beginner that should not be is the Chinese algae eater. Hell, these fish shouldn’t be sold to anybody. They are also mass-produced in Southeast Asia nowadays and so are sold as inexpensive algae eaters. But they really don’t eat all that much algae. Instead, they seem to prefer to suck the slime off of other fish. And the older they get, the less algae they eat, and the more slime they suck. They are also prone to extremely hyperactive behavior (try catching one with a net sometime) and sudden death (from heart attack?). In a suitably large tank with lots of cover they might settle down to a long life, but after they reach 10cm or so in length they will mercilessly harass their tank mates. I once owned an enormous 25cm monster that was probably the most annoying fish I’ve ever met.

Dwarf gouramis. There has been an explosion of new color strains of dwarf gouramis around lately, again thanks to Southeast Asian breeders. And so nowadays pet stores will have several tanks of colorful dwarf gouramis at low prices. But I would not recommend them to the beginner. They are very shy fish that really can’t compete with the barbs and tetras the beginner will likely put them in with. Give them their own well-planted tank in a quiet corner and they are wonderful fish. In a tank without much cover (but with lots of tiger barbs) they will be thin, pale, and unhappy.

The most common fish purchased by the beginner is the goldfish. There are two things that could be wrong with this. First of all, many beginners try to mix goldfish and tropical fish. This is never a good idea, and goldfish should not be kept at temperatures above room temperature. And the second problem is that practically all beginners fail to give their goldfish enough room. Adult goldfish need at least 100 liters of water per fish. Not even one can be housed in the typical beginner’s sized tank for the long term. But for the beginner who keeps goldfish at a suitable temperature in a suitably large tank or pond, goldfish are very good fish indeed. Just stay away from those grossly malformed varieties that can’t even swim properly anymore. Like all fish that have resulted from such misguided breeding programs, their genetic soundness is absolutely miserable.

That’s everything I would recommend the beginner not get. But what should they get?

Fish Make Babies,how ?

Fish breed in many ways, and yes you can watch. In fact, watching fish breed is one of the great fascinations in the hobby because there are so many interesting breeding strategies among fish.

There are two main strategies that fish use: egglaying and livebearing.

Livebearing fish do what the name suggests. The female gives birth to fully formed, free-swimming young. The female fish is internally fertilized by the male fish, and carries the fry for about a month before delivering them. Upon delivery, the babies swim off, hide, and begin searching for food.

Livebearers include the popular mollies, platies, swordtails, and guppies. Other livebearers are halfbeaks, anableps, and fish in the Goodeid family. They are easy to sex, as the female is larger, and the male has a rod-like anal fin called a gonopodium that he uses to internally fertilize the female. After fertilization, the female can produce multiple batches of babies without a male present.

Egglaying is also what the name suggests: the fish lay eggs instead of giving birth to little fish. As the fish grow, they hatch into fry with an attached yolk sac, and then mature into fish. The process usually takes around a week to 10 days, although it can vary widely.

Egglayers have many methods of laying their eggs
Egg scatters usually scatter eggs around weeds, or onto gravel. The male chases the female during spawning, and the eggs are fertilized as they fall. Spawning runs can be spectacular to watch since the fish race around the tank and ignore anything else, including food. Examples of egg scatterers are tetras, barbs, rasboras, and danios.

Substrate spawners are a little choosier about where they put the eggs. They lay eggs that attach to some sort of substrate. Plants, rocks, wood, and even the aquarium glass may be chosen as a spawning site. Both fish participate in the egg laying, with the male fertilizing the eggs as the female lays them. Examples of substrate spawners are many catfish, some cichlids, and killifish.

Bubblenest builders lay their eggs in a nest of bubbles blown by the male fish. The bubbles are held together with saliva and look like foam. They tend to attract infusoria that the babies can eat, and keep the eggs at the surface of the water, where they are well-oxygenated. The eggs are laid a few at a time, and carefully placed in the nest where they hatch. Examples of bubblenest builders are bettas and gouramis.

Mouthbrooders actually keep their eggs in their mouths until the eggs hatch. The eggs are again laid a few at a time, and once the male fertilizes them, the parent doing the mouthbrooding gathers them up in his/her mouth. That parent eats sparingly, if at all, until the baby fish are released. Examples of mouthbrooders are male arowanas and female cichlids.

Marine fish also lay eggs. Some are substrate spawners, but many lay pelagic eggs that float in the plankton. There the eggs hatch into a larval stage, and the larvae float freely and eat tiny plankton until they grow into fish. See the Moe reference for a more complete description.

Breeding and Agression

``Help! Why have my angelfish (or kribs or African cichlids) started killing everything in my tank?''

``Why did my female platy just turn around and eat her babies?''

``I think my tetras spawned. Where are the eggs?''
Parental care in the fish world varies widely. Parents can be anywhere on a continuum from eating all their eggs or fry, to both parents fiercely guarding their eggs and fry.

Many fish parents show some common behaviors, so I will discuss them here.

Most fish consider any and all fish eggs and young to be a tasty treat. Therefore most fish will not hesitate to snack on any they find, including their own. This means that egg scatters and many substrate spawners really cannot be bred in a community tank, as the eggs will quickly be eaten by the parents and other fish. Marine fish and invertebrates also eat eggs. Livebearers are especially notorious for eating their young.

A few fish ignore their eggs or fry, and so can be bred in a species tank. White cloud minnows can breed this way, and many killifish will at least ignore the eggs. Baby killies are fair game, though. Guppies will also often ignore babies.

Other fish have one parent that guards the eggs and fry. Most bubblenest builders and mouthbrooders operate this way, as do some substrate spawners. The responsible male or female stays with the eggs and young, until they are free swimming. With bubblenest builders, the male tends the nest, blows bubbles as they pop, and keeps any falling eggs or fry in it. He will also defend the nest against other fish. Mouthbrooders simply hide their eggs in their mouths, and some substrate spawning catfish will hide the eggs underneath them. Certain substrate spawning cichlids also have one parent care for the eggs and fry.

A more common setup among cichlids is to have both fish guard and care for the young. This setup can be really fascinating to watch. The parents will take turns fanning or blowing fresh water onto the eggs, and removing any fungused eggs. They will also fiercely defend the spawning site, which can often cause injury or even death to other tankmates. Once the eggs have hatched, the parents will also guard the fry. Some fish will even move the fry to a different place each day. Once the babies are free swimming, some fish continue to guard them, while others end their parental duties. Many African cichlids guard their babies until they spawn again. Discus even feed their babies off of their slime coats.

A more extreme version of guarding is practiced by some Tanganyikan cichlids. There, older siblings will stay around the nest and help the parents defend subsequent spawns. The babies are allowed to stay until breeding age, when they are driven off.

Breeding Tanks

``My fish just laid eggs. How do I keep the eggs or babies from being eaten?''
The most common way to keep eggs from being eaten is to use a separate breeding tank. There the parents can spawn or give birth to their young, and be removed once they are done. Egg scatterers can be placed over a piece of netting, a grate, or a bed of marbles to protect the eggs as the fish spawn. Bubblenest breeders and mouthbrooders can be left in the tank until they stop caring for the young. Livebearers can be allowed to give birth in a dense thicket of plants or plastic spawning grass, so the babies can hide until the mother is done giving birth and is removed.

A breeding tank also is good because it can be kept clean. Eggs and fry need very clean water to hatch and grow. There are also no adults around to compete with the babies for food. Many breeders use a bare tank with only a sponge filter as filtration. Debris and extra food are easily seen and siphoned off daily. Frequent water changes can be done on the tank, as there are no other fish around to stress.

Another solution is to allow fish to breed on yarn mops, a plant, or a piece of slate or glass in the community tank. The eggs can then be moved to the breeding tank to grow. This works well for angelfish, catfish, and Australian rainbowfish. Killifish eggs can be collected from peat or yarn mops and set in a separate container or dried to incubate. Livebearers can be bred in a commercial breeding trap or breeding net within a community tank. The trap separates the babies from the mothers and then gives the babies a safe place to grow.

Some cichlids protect their babies well enough to just be left in a community setup, although this can stress the other fish in the tank. In fact, there are species of cichlids that will turn on each other if there are no other fish in the breeding tank for them to threaten.

Breeding Requirements

``I have fish in a breeding setup, but they just won't breed.''

``Why do my fishes' eggs keep fungusing and the fry dying?''
Many fish will not breed successfully without specific requirements. These include:
A mix of male and female fish.
I know this sounds obvious, but some fish are not easy to sex. In species that are difficult to sex, is best to start out with at least six young fish so that you are certain of getting both males and females. Starting with many fish also gives monogamous fish a chance to pick compatible mates. Sometimes if a single male and female are introduced, they will not breed. Other fish, like livebearers, killifish, and polygamous cichlids need more females that males so that females are not harassed by amorous males.
Extremely clean water.
Most fish will not breed if there is any ammonia or nitrite present, and large amounts of nitrate are toxic to baby fish. Some fish, especially tetras, must be bred in a breeding tank that is bare and sterile so that their eggs do not fungus. For more information about clean water, see the beginner FAQ.
A varied diet.
Fish that are producing eggs need better food that fish that are just living in a community. Breeders call the process of specially feeding parents conditioning. Conditioning foods include live foods, fresh frozen foods, or spirulina based foods. Find out the specific requirements of the fish you intend to breed. If you need information about live foods, see the live food FAQ.
The correct environment.
Fish that breed on substrates need proper substrates to breed on, like peat, rocks, shells, or plants. Some fish are shy and require a lot of cover, caves, or dim light. There are also fish that require a particular water chemistry to breed. Examples are discus, which require very soft, acid water or African cichlids which require very hard, alkaline water.
External cues.
Many tropical fish breed in the rainy season. When it rains, streams flood, the water hardness drops, and there is thunder and lightning. Adventuresome breeders with rainy season fish may try large water changes with distilled water, watering cans to simulate rain, strong currents, and even flashing lights and loud noises. Temperature changes may also stimulate spawning, as may changes in the light/dark cycle.

Raising Fry

``My fish bred, but I cannot raise the fry to adulthood.''
Rearing fish can take some work. Baby fish require clean water, and some require special foods.

Baby livebearers are usually the easiest to raise. Some will take finely crushed flake foods from the start, and only require frequent water changes to keep up with their growth. They also need algae or spirulina.

Baby egglayers are often more difficult to raise. Most are too small to eat adult fish foods, and so require special foods. Live baby brine shrimp are the food of choice for most baby fish, although some require even smaller infusoria. Sifted daphnia also work. Baby algae eating catfish require algae or blanched vegetables. There are also commercial fry foods that work or, in desperate situations, cooked egg yolk. Be careful, though, because non-living foods pollute the tank water terribly -- especially egg yolk.

Actually, keeping the tank water clean is probably the biggest challenge in raising fish. The growing fish require lots of food, and they are not very good at finding it which means even more must be added to the tank. As in any fish tank, adding lots of food must be balanced with keeping the water quality extremely high. In fact, fry require cleaner water than adult fish. Frequent water changes are a must, as is efficient biological filtration. Baby tanks often require daily water changes of up to half the tank. Sponge filters are the preferred method of filtration because they are great biological filters but cannot suck up baby fish.

Marine fish larvae have the strictest requirements of all. They must be fed extremely small plankton or rotifers in a tank with near-perfect water. For more discussion of marine fish rearing, see Moe.

Finally, as the baby fish grow, they must be transferred to larger quarters. Clearly the 10 gallon tank that housed 100 fry cannot house those 100 fish for long. Betta breeders have even more work on their hands, since the little male bettas will fight and have to be put into separate jars or a partitioned tank.

``I have a ton of baby fish. What do I do with them?''

``Can I make any money breeding fish?''
Finding homes for baby fish can be almost as much of a challenge as breeding them. Young fish can be given away, auctioned at aquarium society auctions, traded for other species, or sold. Pet stores will sometimes take African cichlids, guppies, and bettas, but many only give store credit rather than cash.

As for turning breeding into a commercial venture, remember the laws of supply and demand. For most common community fish, pet stores can order whatever they want whenever they want it from importers, fish farms, and wholesalers. The hobbyist, on the other hand, has occasional batches of fish that the store may not need or want at that time. The only thing on your side when you walk into a store with a batch of unrequested fish is that locally bred fish are often healthier and less stressed that fish that have been shipped and must be acclimated to local water conditions.

If you insist on breeding saleable fish, try rare catfish, rare rainbows, African cichlids, show quality fancy guppies, or marine fish. Those are all difficult for stores to obtain. To make money selling more common fish like angels, barbs, tetras, cory cats or livebearers (other than guppies), you need many breeding tanks and breeding pairs of fish to assure a constant supply. You must also have fish of consistent quality.

Personally, I would recommend that you breed fish for the sheer pleasure of it, rather than turning your fun hobby into a business venture. There is nothing like seeing a pair of cichlids court, disappear into a cave, and emerge in a few days with a swarm of babies.

Breeding Fish

Why breed fish?
There are many reasons. In our club, you get points in a nationally recognized Breeder's Award program. If I ever move to another area of the U.S. there's a good chance that a new club I join will accept the points I have earned at YATFS. Some people think they going to get rich - or at least support their hobby - selling the fish that they breed. Others do it for the scientific interest and fulfillment of seeing different species procreate. What better way to appreciate the "grander scheme" of life? And how about the ease of teaching the little humans in the household about the birds and the bees? (Although I must confess, I thought briefly that I had missed the boat when my then 4 year old daughter asked if the pregnant cat was an egg layer or a livebearer.) Still others do it for the competition within the club. On the larger scale, they compete to spawn species that are considered difficult or have never before been done.

How do you spawn fish?
First, you do some basic research. Read and/or talk to someone who already spawned the species. Find out what kind of species of fish you have. Is it a livebearer or egg-layer? What is the best ratio of males to females for that species? What is the best spawning age for the fish? What are the ideal tank conditions?

You also need to find out the best way to care for the fry. Some need to be left with the parents for a while. Others need their parents removed to prevent cannibalism. Some require special foods the first week(s). Others can subsist on average flake foods.

This article is not all inclusive. There are many fish that are considered "odd-balls." They break the rules and do not fit into any one category. They exhibit one or more unique spawning traits to set them apart from the others. That is why breeding fish is so intriguing to many of us. There's always another challenge or adventure in the hobby.

Livebearers

You usually can't tell exactly when these fish have spawned. The male constantly chases the female. The eggs are fertilized inside the female's body. The male transfers the sperm into her vent with his modified anal fin, called a gonopodium. But, if you know the average gestation period for the species and you watch the female's developing belly size and shape, you can estimate when delivery will take place. Gestation for livebearers can be from 25 - 45 days. Most, but not in all, livebearing female fish have a gravid spot near the base of their tail, which is a sort of window to the developing fry. A day or so before delivery, you can sometimes see the babies' eyes. Some species get a very square looking chest right before delivering. The most important reason for knowing all this is to know when to remove the female to a separate delivery tank. Sadly, most livebearers will eat fry. Even their own.

Another trick with livebearers is that females can store sperm from previous mating for many months. Just because you lost the male doesn't mean the female will not any more babies. Also if you want to breed female A with male B, you may have to make sure that she is not with any other males whatsoever. Granted, the most recent male will most likely be the father of the fry. But it is always better to be extra careful with livebearers.

Generally speaking, the delivery tank should be 2.5 - 5 gallons. Use 70% water from the original tank, a sponge filter and a heater if needed. Live floating plants or artificial "spawning grass" will give the fry somewhere to hide. Lowering the lights will calm the female. Some theories say you should avoid exposing the gravid female to the air. So use a jar to scope her up and transfer her in water to the delivery tank. As soon as she is done delivering, remove the female back to either the original tank or a recovery tank away from the attentions of the male. Some species take up to 3 days to deliver their entire brood. Still others deliver a couple fry every 5-7 days. Again do some research.

Most livebearer fry can be feed crushed flake food from the day they are born. But all love baby brine shrimp and microworms! They are generally larger than egg-layer fry and are free swimming almost immediately. Therefore, they do not require parental care.

Egg-Layers

As mentioned before, egg- layer fry are often small and require special foods and/or varying degrees of parental care. Do the research. As far as spawning, these fish are divided into seven basic groups according to their different spawning styles:

Open substrate spawners
This is the most common spawning method, mainly used by cichlids. These fish often form permanent pair bonds. The female lays the eggs on a flat surface, such as a rock . The male works in close proximity with her to fertilize the eggs. These fish are often very good at guarding the eggs and defending the fry. Angels, Discus, Severums, Jack Dempseys, Oscars, Firemouths, Jewel Cichlids, Rainbow Cichlids, Rams, many Aequidens species, Sunfishes, Darters, Gobies, Damsels & Clowns.

A compatible pair must be found. This is best done by raising a group of 6-8 fry to maturity and picking out the pairs as they form. Set them up in their own tank, condition them, watch & wait. If the pairs become regular egg-eaters or fry devourers, you can remove the eggs to be hatched away from their parents.

Although these do not technically hide the eggs like the next category, some will often bury them and move them from place to place in the tank. So don't think you lost the spawn until well past the time when you should see them free swimming. In addition, although this group are not considered Mouthbrooders some will pick the fry up in their mouths and move them to a safer territory, especially at night time. Don't think they are eating the fry until many are actually missing!

Substrate Spawners that Hide their Eggs
Several of these fish also form permanent pair bonds. Most however, do not; it is the female that takes on the care of the fry. Eggs are usually laid in a hidden area such as a cave, flower pot or shell. Because of their secretive nature, the spawning is usually not observed.

Included in this group are many Dwarf cichlids, Apistogramma, Nanacara, Namachromis, Pelvicachromis, Julidochromis, Lamprologous, Loricaria, Farlowella & Ancistrus. It is interesting to note that the males of the catfish species are the ones that take care of the fry.

Set up a pair with several spawning choices. Feed them well and wait for Nature to takes it's course. The female will lay the eggs within a cave or under a rock and the male will fertilize the eggs in unison. Sometimes you guess if spawning has actually taken place or not because the female disappears for about two weeks while she tends to her eggs. She drives the male out during this time. When the fry are free- swimming, she will bring them out and parade them around the tank. Pay attention to feeding whatever the fry require. It is often good to remove the male at this point. In another 3-4 weeks, the female can also be removed.

Mouthbrooders
An easy group of fish to spawn because they protect the fry the most efficiently. Also, they tend to be a very hardy group.

Set up a pair with rocks, gravel and caves. A few dither fish will help them keep their aggressions away from each other. Feed them well, Usually the male digs a pit in the substrate. The female, when ripe, will begin the circular spanning dance around the pit with the male. Eggs are laid, fertilized, then scooped up into the female's mouth. In some African Cichlids the female tries to " scoop up" the egg spots on the male's anal fin, thereby ensuring that the sperm has reached the eggs in her mouth. The eggs are incubated in her mouth for about three weeks. She will not eat at all in this time, unless the eggs have been lost or swallowed. Wait for about two weeks and move her to another tank. When the fry are old enough, the female will release them and guard them. Often, she can be seen chewing up and spitting out food for them. When danger approaches the fry fly at lightning speed to hide in the mother's mouth. When the young have been free swimming for about three to four weeks it is OK to remove the female. Sometimes she will eat them if she is ready to spawn again.

Egg Scatterers
This group consist mainly of those fish we call schooling types: Barbs, Danios, Characins, Tetras & Rainbows. They spawn as they school, scattering eggs all over the tank. The females release the eggs haphazardly; the males follow close behind, releasing sperm at the same time. Amazingly, the two meet and the eggs stick to whatever they land on. The eggs are usually eaten as fast as they are laid by the spawners and their tankmates.

To successfully save the eggs, set up another tank with lots of plants (plastic or real) or mops. Larger gravel or marbles on the floor also help to catch the eggs. Put in an air stone and a heater, if needed. Introduce a female only, and condition her on quality foods for a few days. One evening , introduce a male. The next morning they should spawn at sunrise. After a few hours, remove the pair. Cover the tank with dark cardboard or towels. The fry will hatch in three to four days. They are very tiny and are often described as slivers of glass on the walls of the tank. They require specialized food (infusoria, APR, etc.) at this stage. In a week or so, they will take live baby brine shrimp, vinegar eels, microworms and such. After two weeks they can take powdered flake foods. Growth will then be more noticeable. Rainbows are in this category, but breeders usually remove the eggs and hatch them like mop spawners.

Mop Spawners
Mainly comprised of Killifish, these fish lay their eggs in mops made of synthetic yarn, or in plants. The goal seams to be to hide the eggs. Included in this group Aphyosemion, Aplocheilus, Epiplatys, Rivukus, Simposonichthys and the previously mentioned Rainbows. What makes these fish different from the egg lay scatterers is that their eggs are harder and larger, and they only lay about 20 -30 a day. Corydoras catfish also seem to fit in this group in method, although they lay many more eggs. Typically, they will attach their eggs to anything in the tank including the mop.

The spawning tank setup is simple enough. Hang several mops, add a sponge filter and a heater if needed. Add a pair of fish. The female will lay the eggs deep in the mop or the plant. The male will then fertilize them. Sometimes they will turn right around and eat them. Another difference with Corydoras is that it is now believed that the female takes the sperm into her mouth and fertilizes the eggs which she is clutching in her pectoral fins, while sticking it on the preferred surface.

You must pick the eggs out of the mop daily and put them in a small container with anti-fungal medication added (methylene blue or acriflavin). Store the eggs in a darker place, at the required temperature. They will incubate for 14-21 days for killies and 7-10 days for rainbows. As the fry hatch, remove them with an eyedropper or pipette to another small container or tank with the correct water parameters and some Java moss or similar floating plants. Some can take live food right away, others need infusoria or APR.

Peat Spawners
This group is made up entirely of Killifish. Cynolebias, Pterolebias, Nothobranchus and Fundulopanchax. These are the fish we hear referred to "true annual" killies. In the wild, they have adapted to life in correlation with the rainy seasons. They hatch, grow and spawn before the next dry season comes along, during which their watery world as they know it dries up and they die. The eggs are able to survive in this drying period. When the next rainy season comes along: life anew.

Set up a 5 gallon tank for a trio of fish. In it should be a bowl that contains about 2" of peat moss. Some people like a slow bubbling sponge filter and some plants or a mop for the female to hide in. Feed the fish well, but away from the spawning container. The male will display himself above the peat moss. When the female is interested in spawning she will come close. They will seem to dive into the peat, where they will lay a few eggs and fertilize them. This continues several times a daily for many days.

Most breeders collect the peat and give the fish a new batch about once a week. The peat is gently squeezed and placed into some newspaper, lightly covered with a plastic bag overnight. The dried peat is stored in a zipped sandwich bag, in a dark place at a correct temperature.

Here is were you need to consult the charts in the killifish books for temperature and drying /incubation time. It can take anywhere from 2-9 months! And incorrect temperatures can cause poorly developed fry or low hatching rates.

When it is time to hatch the fry, the parents are most likely dead. Wet the peat, then submerge it in a couple inches of water in a plastic shoe box. Cover lightly to shade the eggs. With in a few hours, fry can be seen popping up over the layer of peat. Remove them with a pipette and put into another shoebox with a few inches of water and some peat moss or a floating plant. after about 24 hours, the peat can be re-dried for another two weeks. Try to hatch more fry. This can be repeated 1-2 more times. Feed the fry often and well, paying attention to water quality. Because these fish live such short lives, they grow quickly.

Nest Builders
As the name implies, these fish build a nest in which to lay their eggs. Fish nests are built with bubbles, mostly on the surface of the water using pieces of plants. The male builds the nest. The bubbles stay inflated because of a special mucous he has in his mouth when he blows the bubbles. The nest builders are mainly the labyrinth fished such as Gouramis, Paradise Fish, most Bettas and Hoplosturnum Cats.

Set up a separate spawning tank for the pair. A very slowly bubbling, aged sponge filter should be included to culture infusoria for the future fry. A couple snails will do the same thing, along with lots of floating plants. A heater will be needed. Some plastic plants or mops are helpful for the female to hide in. The key to the set-up is an upside down Styrofoam bowl or something similar, taped to the front of the glass of the tank, right at the surface of the water. There should be some dead air space inside the container.

Put the male into the tank, and do not add the female until he has started a bubble nest and she is ripe with eggs. When all conditions are right, the male will entice the female under the nest. He will wrap his body around hers until she releases a stream of eggs. He releases his sperm at the same time. Then he lets her go. She will remain motionless and sink for a moment or two, but the male will immediately go to work gathering eggs in his mouth and spitting them into the nest. When the female comes to, she will often help. This will continue for several hours. When they are finished spawning, the male will violently drive the female away from the nest. Now is the time to remove her.

The male will guard, fix and add bubbles to the nest for the next three days. When the fry begin to hatch, they will wiggle out of the nest. He will actively catch them and spit them back into place. He should not be fed during these 3-4 days. Otherwise, he might forget his job and begin eating the fry as well.

At the age of 6-8 weeks the fry will begin to develop their labyrinth organs. Covering the tank with plastic wrap or taping the cracks in the glass will keep the air temperature closer to the water temperature and you will lose less fry.

Some exception to the surface bubble nest are seen with the Croaking Gouramis and the Pygmy Gouramis. They build their nests inside a cave, so breeders usually use 2" PVC tubing pieces for them.

This Overview should be enough to get you interested in spawning some of your favorite fish.