Breeding Aquarium Fish

What Do I Need to Know About Breeding Aquarium Fish?



Depending on the species, breeding aquarium fish can be tricky. In order to increase your chances of a successful spawning it is best to condition a pair of sexually mature adult fishes and to introduce them into a breeding tank. On the other hand, some species – particularly livebearers like guppies and swordtails – are likely to reproduce in the community tank with little to no effort required on your part. If you are looking to encourage your fish to spawn, however, there are a few things you can do. You should begin by researching the particular species you hope to spawn to determine whether they have any particular requirements in regard to their conditioning or the breeding tank itself.

Selecting and Conditioning a Pair

Before you can select a breeding pair to condition for spawning you must learn how to tell the two sexes apart. This can be difficult in some species but there are some general things you can look for. In many species of freshwater aquarium fish the males grow a little larger than the females and they also tend to be more brightly coloured. For more detailed information regarding sexing aquarium fish it is best to research the particular species you are trying to breed. Once you are able to tell the two sexes apart, select one healthy specimen of each sex. The fish should be of normal size and they should display healthy coloration. Keep in mind that some species are more likely to spawn in groups rather than pairs so look for this information while researching the species you are hoping to breed.

In order to increase your chances of a successful spawning it is wise to condition your breeding pair on nutritious live and frozen foods. The male and female fish should be conditioned separately, before they are introduced into the breeding tank. In egg laying species, you will know it is time to put the fish in the breeding tank when the female’s belly becomes visibly full with eggs. Once you have placed the adult fish in the breeding tank, spawning may occur quickly or it could take some time. Observe your fish closely to be sure the male does not overly antagonize the female. The males of some species, especially betta fish, can be extremely aggressive during breeding. If the female becomes injured or worn out by the advances of the male before breeding occurs, remove the female from the tank and give her a day or two to rest before putting her back in.

Setting Up the Breeding Tank

Also called a spawning tank, a breeding tank is simply a tank designated for the use of a breeding pair. Using a separate tank for breeding purposes is essential because many fish will feel threatened by the presence of other fish and will either resist spawning or become aggressive. Having a separate tank is also useful because you can use it to raise the fry once they have hatched. The breeding tank should be about 10 to 20 gallons in size and it does not need to be heavily decorated. In fact, it is best to leave the bottom of the tank bare to make cleaning easier and to make it easier to spot the eggs and fry. Outfit your breeding tank with an aquarium heater to maintain a stable temperature and use a sponge filter to facilitate aeration. Sponge filters are best for breeding tanks because they provide both mechanical and biological filtration without producing enough suction or water current to put eggs or newly hatched fry at risk.

Most egg-laying species of fish prefer to have a few plants in the breeding tank. Egg scatters in particular prefer fine-leaved plants while other fish prefer broad-leaved plants. To determine how to decorate your breeding tank, research the preferences of your particular species of fish. Once you have set up your breeding tank and added the conditioned adult fish you can set about encouraging spawning behaviour through a variety of means. Some fish respond to an increase in tank temperature while others, such as corydoras catfish, can be encouraged to spawn by lowering the tank temperature through cool water changes. It is also important to keep feeding your breeding pair healthy foods to keep them in the right condition for spawning.

Raising the Fry

Once your fish have spawned, it is often wise to remove the parent fish from the tank. Some species, like discus fish, will actually care for their young but many tend to eat their own eggs. When you are researching the particular species you plan to spawn, look for information regarding the parenting habits of the fish. If the fish you are breeding are egg-layers, treat the tank with Methylene blue to prevent fungus from forming on and killing the eggs. Keep the tank well aerated but do not let the current become too strong or the eggs could become detached. It is also important to maintain a stable tank temperature and to avoid cleaning the tank until the eggs have hatched.

The amount of time it takes eggs to hatch will depend on the species, but most eggs hatch within a few days of spawning. After hatching, the fry of many species will feed off their yolk sac for a few days and will not require any food until it is completely absorbed and they become free-swimming. When raising fry it is essential that you feed them often. Small foods like infusoria and newly hatched brine shrimp are the most recommended foods for young fry and you should offer small amounts of these foods several times daily. If you do not feed your fry well during their first few weeks of life it is unlikely that they will ever achieve a normal size as adults.

Once the fry have become free-swimming you can begin to perform daily water changes of between 25% and 50% of the tank volume. To avoid sucking up fry along with the dirty tank water you can substitute a length of aquarium airline tubing for your standard aquarium vacuum. Over the next few weeks, your fry should increase in size and should begin to resemble their parents. Once the fish reach one inch in length you may need to separate them into separate rearing tanks in order to provide them adequate room for growth. This is especially important for species like cichlids that tend to grow larger than other aquarium fish. Once the fry grow large enough that they are not likely to be eaten by other fish, you can introduce them into your main tank or sell them.