Your Corydoras is looking huge and has visible small red lines on her body. Is she ripe with eggs? Dr Michael Hardman advises.
It sounds like your Bronze cory is indeed mature and ripe with eggs. The small red lines are probably blood vessels that serve the ripened ovaries. The vessels become visible as the ovaries swell and press against the body wall — so there’s nothing to worry about there.
In most tropical fishes, an increase in temperature causes the ovaries to develop and the eggs to ripen. Usually, a second cue is needed to release the eggs (ovulation). The classical cue is a 30-50% freshwater change using dechlorinated water a few degrees cooler than the aquarium.
Provided you have two or three mature males per female, a day or two following the water change you should eventually see some eggs.
If your corys spawn and you want to raise the babies, get a breeding net. Once spawning is complete, carefully roll the eggs off the glass or plants and into the net and add an anti-fungal agent.
Depending on temperature, the eggs will hatch in three to five days and then the fry will feed on their yolk sacs for four to five after that. Start adding finely powdered flake or tablet food, better still newly-hatched Artemia or microworm, from day three, a couple of times a day until they are large enough to be released into the aquarium.
This item was first published in the December 2009 issue of Practical Fishkeeping. It may not be reproduced without written permission.