Breeding Freshwater Tropical Fish

One of the attractions of keeping tropical fish is that they may breed in captivity.  Sometimes this happens through a lot of time and effort on your part, or in the case of livebearers, it’s actually hard to stop them breeding!  If you allow breeding to take place in the main aquarium with no intervention from yourself, you may get a few fry that make it to maturity, but their parents or the other occupants will eat the majority of them.  It is generally advisable to set up a separate breeding aquarium to stop this happening.

Preparing a Breeding Aquarium

Freshwater tropical fish spawn in a variety of ways, so the aquarium will need to be set up accordingly.  There will not be many fish in it, so a powerful filter will not be needed, and one that is too powerful may cause a problem to the young fish.  The water should be the same quality and temperature of that in the main aquarium, unless different water conditions are needed for spawning.  If this is the case, gradually change the water over time, so as not to distress the fish.

Egg-scattering fish – are not protective towards their young and will eat them given half a chance.  The main purpose here is to separate the eggs and adult fish as soon as possible, and this can be achieved in a few ways.  A layer of marbles on the aquarium floor will provide fish-proof crevices for the fertilised eggs to drop through.  Thick bunches of plants will trap adhesive eggs and effectively hide them from the adults, or alternatively the fish could be spawned over a net or grill submerged in the water.  Remove the adult fish after spawning

Egg-burying fish – these will need a deep layer of peat, on top of the gravel, on the base of the aquarium, so the fish can dive and bury their eggs.  It is possible to remove the peat after spawning and store it dry for a few months.  Immersing the peat back in water reactivates the hatching process.

Egg-depositors – these fish are very protective towards their eggs and young, but the aquarium will need to be furnished with suitable rocks and caves to provide a choice of spawning sites for the fish.

Bubble Nest builders – these fish will collect fragments of plants to build their nest, give them plenty of plants, and it will also give the female a place to shelter after spawning.  The male will look after the eggs and his young, so the female can be removed from the aquarium.

Mouth Brooders – these are fish where the eggs are incubated in the female’s mouth, so no special requirements are needed here, only peace and quiet.  She will not even eat food at this time.

Livebearers – at birth these young fish are miniatures of their parents, and are free-swimming, but give them an aquarium with plenty of plants, and some floating plants, to give them a chance of escaping from their cannibalistic parents. Remove the mother as soon as possible after giving birth, the male does not need to ever be put in the breeding aquarium.  It is advisable to let the female have a few days to recover before putting her back in the main aquarium.

Selecting and conditioning

Whichever fish you are breeding, firstly you need to find a pair, a male and female.  In livebearers it is relatively easy because the modified anal fin easily distinguishes the male.  In many other breeds the male is slimmer and more colourful.  Fish from the Cichlid family select partners themselves, and any two fish that keep together, excluding others from their area of the aquarium, are likely to be a pair.

Fish selected for breeding should be healthy, free from disease and deformities, and should have strong colouration.  When trying to breed egg-layers, it is often a good idea to separate the fish for a few weeks, and feed both of them on high quality food, with the emphasis on live food.  When spawning time approaches, introduce the female to the breeding aquarium first, so it becomes her territory, and then let the male in, and he has to court her.

If possible, spawning should be supervised.  Some male fish are very active drivers and will continue to harass the female after spawning, other males may not even accept the female as a partner and may attack her.  In both cases, the female will need rescuing.  In most cases the adult fish should be removed from the aquarium once spawning has taken place.

As soon as the young fish begin swimming, they will need food, but do not feed them before they are free-swimming, as they are getting their food from their yolk-sac, and any uneaten food will pollute the aquarium.  Young fish should feed continually, and a low-powered light should be left on to encourage this.  As the fish mature, partial water changes should be made, the aeration rate increased, and the filtration system upgraded.

As the fish develop, any slow developers or stunted ones should be culled, to ensure a high quality of fish is maintained at all times.