Breeding Fish
It's possible to breed many species of fish in the home aquarium; one day you may wake up and find you have fry without ever having done anything proactive. However, the more you know and understand about your fish and their requirements, the more chance of success you will have. I've compiled a brief outline for breeding some of the more common species.
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Cichlids are either mouth-brooders or substrate brooders. Mouth-brooders store the eggs in their mouths until they hatch, or until the fry are big enough to fend for themselves. Substrate brooders lay their adhesive eggs on stones or plants, and then clean them and fan them until they hatch. The halpochromines branch of cichlids are mouth-brooders, with the female caring for the eggs, whilst the tilapiines display all combinations of parental care. The latter often care for the brood after they have hatched, whilst the former mouthbrooders have a much more difficult and tiring time during normal brooding and tend to abandon the young. This usually occurs after about three weeks. Usually a breeding pair will separate after the breeding season ends, and pair with new fish in the new season. Cichlid breeding is seasonal in the wild, except in areas unaffected by climate changes, such as lakes, where it may be continuous if the food supply is plentiful. Many people find African cichlids can be aggressive during breeding periods, but it is important to understand why. Cichlids like to dig, so you must provide substrate which is deep enough. When building nests, they are also known to be destructive, dragging plants around to create a nest. You should let them do this if you can. Larger items can be weighted down to prevent total destruction of the aquascape! Cichlids also need space, in order to claim their own piece of territory. Lack of space with more than one mating pair will often result in fighting between males.
Catfishes are one of the most diverse fish in existence, with over 2000 known species. Most are tropical freshwater species, but some come from cooler climes or marine waters. Here I've focused on one of the more common varieties. Corydoras can be sexed and bred fairly easily. The males tend to be more slender than the females, with spear-shaped ventral fins. It is recommended that you isolate spawning Corydoras, to protect the eggs from predators. A 10 litre breeding tank with a thin layer of sandy substrate would be ideal, with one or two plants for cover. Filtration is essential for breeding tanks to ensure the young have well-oxygenated water. The males chase the females, whilst the females look for spawning sites. Once settled, the male will position himself in front of the female, so they make a T shape. They will them seem to judder as the eggs are released and fertilized by the male. The female will then lay the eggs on a pre-cleaned flat surface, like a broad leaf or rock, positioned toward the top half of the water, where she can be sure the eggs will get oxygen. This is the time to remove either the adults or the eggs, to prevent the eggs being eaten. Eggs can be removed very carefully with a razor blade, and placed in a net or sieve just below the water surface. The eggs will hatch in about 48 hours. The fry should be fed on Artemia (brine shrimp) initially, moving onto fine flake and Daphnia as they get bigger.
Cyprinids include Barbs, Danios and Rasboras. These are considered some of the easiest fish to breed in captivity. All species are egg-scatterers, abandoning their eggs immediately. This makes the eggs exceptionally vulnerable to predators and the parents, so if you want a successful brood you will have to remove them. They can be placed in a fry net and fed on fine live artemia once hatched. You can generally release them back into the aquarium when they are big enough not to fit in the other fishes' mouths. Be aware that these fish can lay hundreds of eggs in one sitting, so you need to be prepared with plenty of live food ready for when they hatch. Developing a cluster of brine shrimp is a great way to ensure you have fresh food at the right time. You will also need to have enough tank space if you're going to keep them for any length of time. Rasboras tend to make spawning runs through the foliage, sticking their eggs to leaves as they go. This makes them exceptionally easy to handle, as you can simply remove the plant. They eggs hatch in about 30 hours.
Loaches breed in late spring or early summer. They lay their eggs on leaves or fibrous roots and then abandon them. Loaches are fond of fish eggs, so they must be protected even from the parent fish.
Livebearers are so called because they give birth to live young. Once released the parents abandon the fry to fend for themselves. They are most at risk of being eaten by other fish and their parents, so they need to be removed to a nursery net or tank until they are big enough to go back into the main aquarium. Mollies, Paties, Guppies and Swordtails are all livebearers. Be sure to have fine live food (brine shrimp) for the young to eat.
Killifish are more difficult to breed because they require very specific breeding circumstances. However, whilst this is true for some species, it does not apply to them all. Killifish feed on live foods, so a good supply of daphnia and mosquito larvae is required. Good feeding is essential for breeding these fish, so it is necessary to be well prepared before breeding begins. Killifish are egg-layers, known as substrate spawners. They lay their eggs in or under the substrate at the end of the dry season in ponds. This means that as the waters dry up, the adults perish but the young are left in an ideal situation. As the waters dry up, the eggs lie dormant until the next rains, when some will hatch. Some will remain dormant in case the rains dry up again, and will hatch during the next rainfall, to ensure the species' survival. These killifish are often referred to as "annual fishes". Most adults only live for a year because of the dry season, but in captivity they often live longer because the water never dries up.
Breeding killifish requires special tank conditions, mainly soft acid water. To achieve this you will need to prepare the breeding tank with a peat substrate of about 5cm, planted with a couple of broad-leafed plants for cover. The water needs to be mature, so it needs to be prepared before you are ready to add your fish. Sometimes peat will not sink readily to the bottom, so it can useful to boil it first to ensure it will sink. The added advantage of boiling the peat is that it will also kill of any fungus or bacteria which could later harm your eggs. Feed the parents well with plenty of live food prior to breeding. When the female is full of eggs (roe), she can be moved into the breeding tank to settle, a little before adding the male. The male will display his fins until the female is ready to mate. Here you will see the fish clasp together and will go below the substrate or push their eggs down into it. After spawning you will notice the female appears very thin and tired, resting on the bottom. Now you can remove her and any other females to another tank to feed and recover. The male should also now be moved to another tank until the female is ready to mate again.
Now you need to drain the peat and water from the breeding tank, carefully squeezing out as much water as you can, until the peat is crumbly. Now you can sift through it for small brown or white round eggs about 1mm in diameter. If you have eggs, you need to store the peat and eggs in a warm place (the airing cupboard is ideal, at around 22-24 Celsius. A stable temperature is necessary for rearing these eggs, so you must check the temperature regularly. Eggs usually hatch after about 3-4 months.
Before hatching, prepare plenty of live brine shrimp for the fry. Put the peat mix into an aquarium and rain water warmed to about 22 Celsius. After about 24 hours you should start to see your fish! If not, try adding some live food to encourage the process. Remember you can dry out the peat again and repeat the process, in case some eggs still remain dormant.
Some killifish are easier to breed, because they spawn onto plants, leaving their eggs along stems and leaves. Now you can just remove the plants into the fry tank. Check the plants every couple of days and remove the eggs. Place them in shallow containers with some water from the breeding tank so they can hatch. Floating the containers on the aquarium surface will ensure the temperature remains stable. Feed the fry with live brine shrimp. It is essential that the fry containers are kept clean, with small water changes.
For information on how to breed gouramis, please see my article at:
