Corydoras - dealing with successive spawns?

[Mol_PMB]

I've got a specific question, but first let me give you some background.

My Corydoras burgessi keep spawning, at intervals of 1-4 weeks. The spawns are usually fairly small (15 eggs) but sometimes larger (maybe up to 50 eggs).

I've not been very good with breeding Corys in the past, but I seem to be having a bit more luck with these, perhaps because I have learnt from my experiences with breeding Farlowellas.

The parents eat most of the eggs if left in the tank with them, although I have had a single survivor from a couple of spawns. Also the eggs are prone to fungus.

For the last couple of spawns I have moved the eggy moss into a 2-litre external breeder box hanging on the parents' tank, and hatched the eggs there. Hatch rate has been relatively low (20%) owing to fungus, but the fry which have hatched have mostly grown well with a good survival rate. The breeder box allows me to keep them in the same volume of water as the parents' tank while being protected from them, and I can feed them intensively. I've now tried adding alder cones and small red ramshorn snails to the breeder box as anti-fungal measures though I have yet to see if they work.
Once about 15mm long (4 weeks old) I moved the fry into a separate grow-out tank.

I'm now in a position where I have:
- Grow-out tank with 5x20mm juveniles (6 weeks old)
- Breeder box with 2x8mm fry (1 week old)
- Parents' tank with 5 adults and 2 older juveniles, and today's spawn of about 40 eggs.
There isn't really space for another breeder box on either tank.

So, to the questions:
1) If I put the eggy moss in the breeder box, will the 1-week old fry eat the new hatchlings?
2) If that's a risk, I could perhaps move the two fry to the grow-out tank. Would they then get eaten by their larger siblings?
3) Any other ideas?

Many thanks,
Paul

[Bas Pels]

While I only once have raised Corydoras fry, and that because I moved the parents, and later found some fry, I cannot imagine 20 mm fry eating 8 mm siblings. Or 8 mm fry eating eggs.

What I can imagine, however, is lager fry outcompeting smaller ones. That wouild be an argument for adding the eggs to the 2 8 mm fry - as there are only a few larger siblings compared to the other alternative

But, if I was in your position, I would think hard about adding the 20 mm fry to the parents tank, freeing their tank for the 8 mm ones.

[Mol_PMB]

Thanks - thanks a good idea!
I've worked out how to fit a second breeder box to the parents' tank (needed a bit of re-plumbing but I've just made it work) so I have solved the immediate problem that way. But if they keep spawning frequently then the problem will occur again soon and I'll definitely go with your idea then.
Many thanks,
Paul

[Mol_PMB]

Incidentally I am trialling the use of red ramshorn snails as an anti-fungal measure, as proposed in this thread:
https://www.planetcatfish.com/forum/vie ... =6&t=42862
It seems to be working OK so far, though my little snails keep escaping from the breeder box and I need to replenish them from my Moina culture (which is more effective as a snail culture!)