1) First, let’s talk about the tank size
For the smaller corys (pandas, aneus and julies), I always use a 10 gallon tank with no gravel because I like to be in control of the areas that the fish spawn in. By that I mean I don’t have to remove the eggs from the tank – just the spawning corys. Then I can treat the eggs with chemical fungicides without the risk of killing the eggs by moving them… (By the way, that’s how 50% of all cory eggs die).
For the larger corys (sterbi, adolfis and rubuties), I always use a 20 high. You have to take the eggs out of these tanks because you run the risk of the adult corys eating their own eggs.
Now we get to the fun part, how to get the eggs out of the tank without damaging them! Some people scrape the eggs off the side of the tank with a razor blade. I don’t, it’s a no-no! I have seen a lot of eggs damaged without the person knowing it. The best way, I have found, is to use a clear turkey baster or your fingers.
2) Now, let’s talk about filtration and water cleaning
No filter is needed. The fish do just fine with just an airline and an air stone. They like it a bit on the dirty side. After all, all corys are scavengers. Besides, if you put a filter in the tank, that is one more place you are going to have to look for eggs.
3) Conditioning the breeders
There are two ways of doing this. The slow way and the fast way.
The slow way is the best way to get a larger spawn. The slow way involves feeding the fish in colder water so they build up more eggs before they spawn (just shut off the heater, they can take it).
The fast way involves using a lot of chemicals to modify the fish’s hormones. We won’t go into that right now, since that really is not good for the fish. What I do is trick the fish into thinking it is a different time of the year (spawning season.) Note: The fish can spawn five to six times per year.
4) What to feed the breeders to condition them?
Live food and lots of it (black worms, daphnia, wingless fruit flies; and if you can get it or raise it, live adult brine shrimp).
5) How do we trick them into spawning?
First you need to drain the tank of at least 50% of its water. Next, continue to feed the breeders the live food we talked about earlier. Leave the tank like this for at least three days. After the three days have passed, refill the tank with a sloshing motion on top of the water (at night is best, with 65° water from the tap). This will imitate a heavy rainstorm which should trigger the start of spawning season. If successful, you should see cory eggs in the morning just after dawn, or in the first couple of hours after dawn.
6) Spawning medium
I have found that the wild stock (sterbies, adolfis and rubuties) need some kind of floating plants to lay eggs on. The normals (tank raised) don’t care where they lay their eggs (on mops, stones or on the glass).
7) Now that you have eggs, how are you going to hatch them?
You can either:
a. Remove the eggs and put them in a bubbler.
b. Remove the adults and treat the whole tank.
c. Do nothing and hope the adults will not find the babies.
The answer is: A or B, but never C.
8) The last, but not least, important thing is what to feed the baby corys?
a. Green water.
b. Micro worms.
c. Baby brine shrimp.
The answer is: A through D in that order.
Editors note: For most species use a ratio of 1 female vs 2 males to get the best results.
First Publication: The Informer, Green Water Aquarist Society of Chicagoland, Maart 2004
Source:Aquarticles (no longer available)
Copyright image: Edwin Kluinhaar