Breeding Fish FAQ – part II

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. Bubble nest breeders and mouth brooders can be left in the tank until they stop caring for the young. Live bearers 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.

Breeding Fish tanks

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 rainbow fish. Killi fish eggs can be collected from peat or yarn mops and set in a separate container or dried to incubate. Live bearers 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 live bearers, 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 breeding 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.

By “Mr. A. Non c/o Calypso”
Article donated by Gerald Jennings of

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