One of our readers would like to breed some albino corys. Fish expert Bob advises on the best way to do it...
Q) I'd like to breed some albino corys. What's the best sized tank for this and should I remove the adults after they have spawned? Any advice on feeding the youngsters would also be welcome.
A) BOB REPLIES: Most albino corys are a form of the Bronze catfish, Corydoras aeneus. These are one of the easiest species of egg-laying fish to breed but they still make a satisfying project, and the resulting young fish should be easy to sell on — unless you want to keep a big shoal of corys for yourself, of course! For breeding purposes, you won't need a huge tank: something around 20l should be fine. Set up the breeding tank with an air-powered sponge filter, using a squeeze of 'gunk' from an existing mature filter to kick start the filter bacteria. The temperature should be around 25°C. These are very adaptable little fish, but a pH around neutral and water that is slightly soft is probably best. A thin layer of sand on the base is beneficial in my experience for raising fry successfully. Adding some plant material like Java moss can also be helpful, but not vital.
It's quite likely that mature albino corys will breed in your main display anyway, so you could simply wait until they do, then carefully remove the eggs and transfer them to the breeding tank. But there is a risk of the eggs being eaten by parents or tankmates before you have the chance to do this. So, to give you a better chance of success, simply pick a well conditioned trio of two males and a female (the females are larger and plumper than males), and transfer to the breeding tank, where you can feed them up a bit with choice foods. To trigger breeding, carry out a 50% water change with cooler water. Once spawning has happened, move the parents back to the main display tank. Some fishkeepers recommend adding alder cones to the tank to help prevent fungus on the eggs.
The eggs typically take around three days to hatch, at which point the fry will live off their yolk sacs for a few days until they become mobile. At this point you should provide tiny live foods, such as micro-worm, or tiny amounts of commercially available dry fry food. A slightly 'grubby' tank, with a thin layer of mulm that you would usually try and remove in a display aquarium, is actually helpful at this stage, as it contains micro foods for the fry to eat. Keep a close eye on the water chemistry and carry out small, regular water changes as necessary. The fry should be quick growing, looking like miniature versions of their parents within a month or so.