Breeding fish is one of the most rewarding aspects of the hobby, from live bearers to egg layers, egg scatterers and mouth brooders there are almost as many ways of reproduction as there are species of fish.
What Fish to Breed?
If you’re hoping to get a pair of fish, pop them in a tank and start producing hundreds of fry, which you can then sell on at a vast profit and make your fortune, then think again. Fish breeding will take time effort and money, for most breeders fish breeding is a side hobby that may just about pay for the extra electricity that running all the tanks will take.
So with this in mind choose fish that interest you. Do you want to watch fish build elaborate nests and raise their fry together? Then consider a cichlid species. Do you want to enter your fish in shows then see what strains catch your fancy? Many species of fish are easy to breed, whilst others are almost impossible, with only one or two people worldwide successful in having raised fry.
Once you’ve chosen your fish and lo and behold they’ve got fry, then the hard work starts. Assuming that either the species you chose doesn’t take care of their fry, or you’ve decided to raise them yourself.
Housing the fry
You can either transfer the fry into a tank filled with water taken from the parent’s tank, or you can remove the parents.
The hardest part about keeping fry alive is keeping the water clean. With this in mind many breeders keep them in a bare bottomed tank with no decorations. Some fry however don’t like the bare glass and so a thin layer of sand can be beneficial.
Rather than move the fry as they grow it can be best to put them in a large enough tank in the first place. Filter with an air driven sponge filter rather than an internal or external filter which may suck up the fry. The sponge may also house algae and other food sources for the fry.
Small regular water changes are the most important, as well as keeping the water parameters steady.
Fry hatch or are born in a variety of sizes from tiny through to large enough to take crumbled flake. There are a range of commercial fry foods available but these are expensive if you have a lot of fish to raise.
Live foods are the commonest types of food feed to fry by breeders.
Vinegar eels are tiny organisms that are useful for tiny fry.
Walter worms, banana worms and micro worms are all different sizes of worms or worm like creatures that are easy to grow on and are a great food source.
Brine shrimp can be hatched easily using an old plastic bottle, an air stone and an air pump, baby brine shrimp (BBS) make great food for small mouths, whilst it is possible to feed the brine shrimp and grow them on for larger fry this is more difficult.
Daphnia and blood worm are readily available from fish stores, and daphnia especially is easy enough to grow on yourself as an ongoing food source.
Many keepers put buckets of water outside to collect mosquito larvae that will grow in there in the summer months, but some aquatic insect larvae predates on fry, specifically dragonfly nymphs.
Grading and culling
Often fry will grow at different rates, and the larger may become able to eat the smaller, even if the difference isn’t this big the larger ones will still be able to get more of the food than the smaller. It’s well worth separating the fry by size.
The other and less pleasant aspect of breeding fish is culling some of the fry. There are a number of reasons to do this.
Deformed fry: in many species of fish the gene pool is limited and often the fry are born deformed, assuming that you don’t have unlimited space to raise on an unlimited amount of fry, its more common to cull these immediately. Even if you have the space is the fry are suffering it’s important to cull them.
Wrong colours/Shape/characteristics: for many fish the colours that are desired in the aquarium are unusual colour morphs, for example goldfish will frequently have young that revert to the wild bronze or silver colour. For some species e.g. koi the first cull can be around 1 in 30 fish, and that means in in every 30 fish survives, the other 29 are mashed up and fed back to the other fry, or other fish. This may seem heartless, but for some breeders to get 20 good fish each year they start with 4000-5000, would you have space for 4980 unwanted fish, every year. Some species will breed closer to the original form, such as many cichlids, meaning that you have a lot fewer culls required.
This isn’t meant to be an in-depth look at the genetics of fish, but the basics.
Dominant and recessive: Fish have two pairs of genetic material, some traits are dominant, some are recessive, and others can exist side by side. Many of the more unusual colour traits are recessive, meaning that both parents have to have the gene, to be able to pass it on to 25% of their off spring.
Albino variety’s and electric blue are two examples of recessive colour traits. In some fish if they show this colour they are infertile, meaning that to breed them you will need parents who both carry the genes of these colours and breed them, half the off spring will carry the genes, 25% will be normal and 25% will show the colours.
Selling your fish
It is legal to sell your own fish if they are just unwanted extras in your tank that you bred in small scale projects, once the scale of your selling is enough that you might be seen to be making a profit you may be seen as a pet shop and require licensing from your local authority.
It is legal to sell fish on most websites, but a good way is at auctions held by local fish groups. These are specifically set up to allow breeders to exchange blood lines and sell off excess stock.