I attended a talk by Ian Fuller last Monday on cory breeding. Now, almost anything he said can either be gleaned from other threads here or is too complicated for me to go into in full, but one thing he said I thought was worth posting here:
In the tank in which you are hatching your cory eggs, put a couple of alder cones, if you have them available. They grow wild in most of the world where the temperature is not tropical. These have anti fungal properties that will keep you from needing to use methylene blue. The cones are clearly visible in the second image in the wikipedia article for Alnus glutinosa
, the Black or Common Alder.
Where I come from (New England), they grow along lakeshores and creeks, and there are always a ton of little saplings (we called 'em weedy bushes).
In any case, Mr. Fuller tends to do his hatching in relatively small containers - 3 to 5 gallons at a guess, and in each he puts a couple or three alder cones and a layer of oak leaves.
Take it for what it's worth. I'm going to give this a shot next time I'm breeding cories.