Breeding Aquarium Fish
Breeding fish is not as dull as it may sound. I remember how paternal I felt when my guppies had puppies - or fry as they are called in the industry. It was all very exciting at first. Then the unmentionable happened: infanticide. The guppies gulped the puppies with glee.
Had I known what to do beforehand, I may have been able to avoid the guppy gobbling. Oh, the memories that haunt me! Still, breeding fish is a lot of fun and here are some hints to get you started.
How do fish breed?
Fish either produce live young or eggs. Guppies, Swordtails and Mollys, are live bearers and are easy to breed. A female Guppy will give birth every four to six weeks and produce up to thirty young at a time. Live bearers are the easiest to start with for the novice.
However, the majority of fish breed from eggs. Even with egg bearers, there is considerable variation in the way in which the eggs are propagated.
Many fish, including Goldfish, Tetras and Zebra fish, are egg scatterers. These fish scatter their eggs spontaneously around the tank as they swim. In a stream or creek, the eggs would be safely swept away but in an aquarium, the eggs are often eaten by the adult fish. This is a common problem with Goldfish. Placing pebbles or marbles in the bottom of the brooder tank provides places for the eggs to rest and develop, out of the way of the adult fish. Goldfish eggs will also stick to plants in the tank. Once the fish has spawned, the plants can be removed to a nursery tank for development. Goldfish eggs take from three to six days to hatch.
Fish such as Cichlids deposit their eggs on broad-leafed plants, on overhanging rocks or in small plant pots placed in the tank. Splashing Tetras will even lay eggs on the leaves of plants just above water level, to protect the eggs from other fish predators. To prevent the eggs drying out, the male constantly splashes the eggs with water by flicking his tail - definitely Sensitive New Age Dads
Siamese Fighting Fish produce a wonderful nest at the water surface from bubbles of saliva and plant debris. Their eggs are deposited in the nest. The male then chases the female off and protects the eggs on his own. Bubble nests are also produced by Gouramies.
The early steps
Many fish will breed with no particular intervention from the aquarist. This is especially so with Guppies. For others, locate a pair that are already showing courting behaviour. A breeding pair is often noticeable because of the interest they show to each other. To stimulate interest in each other, fish of the opposite sex are often separated prior to mating. This is easily done with a glass partition in the aquarium. While they can wink and smile at each other coyly, they cannot cavort. To modify the old adage, ‘abstinence makes the heart grow stronger’ and when the partition is finally removed, the pair are more likely to propagate.
The fish can be brought into peak condition by feeding them good quality food, especially live food, prior to breeding.
For those that lay eggs, careful observation at the time of spawning (egg laying) is important. Male fish often show too much attention to the female and they need to be separated after spawning has occurred. In other cases, the fish and their eggs will need to be separated to prevent the fish from eating the eggs.
Also, some male fish show almost continual interest in females while they attempt to determine if she is receptive. Plants, rocks and other tank ‘furniture’ provide refuges for the females and the larger the tank, the more room she has to escape. For some species, having many females housed with a small number of males forces the male to share his interests and so no particular female fish is excessively worried.
Feeding the fry
Do not give food to your new brood until they are able to consume it otherwise the food will decay and pollute the tank.
While the young of live-bearing fish will be able to eat immediately, the young of egg-laying fish often remain immobile for several hours while they feed off the remainder of their yolk-sac.
Commercially available fry food comes in liquid or powdered form. The size of the particles must be such that the fish can eat it and for this information, you should consult your aquarium shop.
Brine shrimp are commonly fed to new fry but they can also be fed microworms and infusoria. Microworms are cultured from a mixture of corn flour, water and yeast. Infusoria are a collection of ciliated protozoans that can be produced by pouring boiling water over dried hay or green lettuce leaves in a jar. Keep the mixture in a warm, dark place for a few days and a healthy broth of Infusoria will be produced in the scum floating on the top of the mixture. Small quantities of the Infusoria can be added to the brooding tank several times a day.
Fry do best on several feedings a day. Only small amounts of food should be given as leftover food will spoil and affect the health of the fish.
Breeding fish can be surprisingly rewarding and your vet or local aquarium shop will provide you with all the details.
By Dr Cam Day BVSc BSc MANZCVS (Veterinary Behaviour) Full-time pet behavior veterinarian - Last updated 16 November 2012
