Corydoras Catfish are relatively easy to breed. Lowering water temperature does the trick!
Water chemistry: Corydoras catfish are very tolerant of water conditions and temperature. A PH of 6.6 -7.0 is fine. For breeding purposes, we will be lowering the temperature of the water slowly down to 65 degrees F.
Sexing Cory Catfish: These fish are not easily sexed. If you have a keen eye, it is possible to tell mature males from females by comparing fish. The males are more streamlined then females. Females have a more compressed body, are thicker at the abdomen (eggs) and higher in structure.
Selecting and conditioning the breeders: Place about a dozen mature Cory's in a 30 gallon or larger aquarium. Keep the temperature at a steady 70-74 degrees F. Feed them a variety of frozen, pellet and live foods 4 times a day. It should take about a month to condition the fish for spawning. After a month, you should be able to sex the fish pretty accurately.
Setting up the breeding tank: For breeding purposes we will need a bare (no gravel, ornaments, rocks etc...) 20 gallon high tank, 100 watt heater, air stone and vibrator pump. Note: No air stone or heater will be required until eggs have been laid. Fill the tank to a 50% water level.
Now we will get these baby's to breed! Select two trios (two males to one female) of breeders and transfer them into your 20 gallon high breeding tank with water of the same temperature as your conditioning tank (70-74 degrees F.). Let them acclimate to their new environment for a few days. Keep feeding them 4 times a day. On the third day or so, start adding slightly cooler water at night to your half filled tank at 2-4 degree increments. One gallon per day should do it. The object is to get the water temperature down to about 65 degrees. If one gallon doesn't bring the temp down enough, try 2 gallons a day. If the fish haven't spawned by the time you get the tank at 100% water level, siphon out 50% and repeat the process. If conditioned properly, they should breed within a few days.
The mating process: Once the fish are in breeding mode, both trios will spawn together. They will lay their eggs all over the sides and bottom of the tank!
You have eggs, now what? Net the adult fish out and place them back into the conditioning tank as fast as you can to keep them from eating their eggs. Place an air stone in the tank and turn up the air full blast. Place about 40 drops of methlene blue or acraflavin fungicide in there to prevent the eggs from attracting infection. Hook up your 100 watt heater and slowly increase the temperature 2 degrees every 6 hours until the temp is about 72 degrees. Keep it there! In about 10 days you will have a few hundred fry swimming all over the place ready to eat.
Feeding and raising the fry: Feed live or frozen baby Brine Shrimp for about a week then a variety of everything. Fine flake food, Daphnia, micro worms etc... You can start changing a little water every day (5%) at this point to freshen things up. Add a sponge filter too. When the fry are large enough in about 3-4 weeks you can add more filtration.
by Jeff O' Corbett
Article Copyright 2007
Video of Cory Catfish Spawning