Why do my cory eggs always get fungus?

[Mississippi fish guy]

My corydoras have spawned a few times lately and each time the eggs get fungus. So far I have tried the following methods to try to hatch the eggs. Eggs were either collected from a spawning mop, a weird hair that I believe has died since then, a plastic plant, real plants, and a specific location on the breeder box that the fish don’t seem to find. I have to use a spawning media because any egg laid anywhere but a dense spawning media will be eaten.

1. I placed eggs in a 5 gallon aquarium with nothing in it. there was a cheap hob filter and an aerator that broke because I dropped it in the water.

2. Using a plastic breeder box that I put some airline in.

3. Bleaching the breeder box, soaking the spawning mops in chlorinated water, and doing a malachite green dip for 10 seconds the day after I collected the eggs because I didn’t get home till 11ish that night and I couldn’t find the malachite green.

Is there anything else I can do or will the eggs keep getting fungus?

[Fish Folk]

On 10/15/2024 at 11:00 PM, Mississippi fish guy said:

My corydoras have spawned a few times lately and each time the eggs get fungus. So far I have tried the following methods to try to hatch the eggs. Eggs were either collected from a spawning mop, a weird hair that I believe has died since then, a plastic plant, real plants, and a specific location on the breeder box that the fish don’t seem to find. I have to use a spawning media because any egg laid anywhere but a dense spawning media will be eaten.

1. I placed eggs in a 5 gallon aquarium with nothing in it. there was a cheap hob filter and an aerator that broke because I dropped it in the water.

2. Using a plastic breeder box that I put some airline in.

3. Bleaching the breeder box, soaking the spawning mops in chlorinated water, and doing a malachite green dip for 10 seconds the day after I collected the eggs because I didn’t get home till 11ish that night and I couldn’t find the malachite green.

Is there anything else I can do or will the eggs keep getting fungus?

Yes. I use over the counter 3% Hydrogen Peroxide (H2O2). I squirt 1 ml. in the egg hatching container every 12 hrs, 3x times total. I also run an air-stone in the hatching container. Infertile eggs always fungus over. But fertile eggs should have a chance that way.

Most breeders prefer using Methylene Blue. That also works. Just don't over-dose. It turns everything blue . . . that's a reason I stopped using it.

You can also use catalpa leaves (Indian Almond Leaves) and Alder Cones to build up tannins in a hatching container. That helps to mitigate fungus.

I've even used a single Neocaridina shrimp for certain species (i.e. Killifish) to fight off fungus.

[Mississippi fish guy]

On 10/15/2024 at 10:18 PM, Fish Folk said:

Yes. I use over the counter 3% Hydrogen Peroxide (H2O2). I squirt 1 ml. in the egg hatching container every 12 hrs, 3x times total. I also run an air-stone in the hatching container. Infertile eggs always fungus over. But fertile eggs should have a chance that way.

My Corys are spawning again do I will try that. Should I still use 1ml since the breeder box is 0.75 gallons? Also should I use an air stone or is plain airline fine?

[Mississippi fish guy]

On 10/16/2024 at 10:08 AM, Mississippi fish guy said:

My Corys are spawning again do I will try that. Should I still use 1ml since the breeder box is 0.5 gallons? Also should I use an air stone or is plain airline fine?