Good question and one I'd love to hear answers for, too: the pair in my breeding tank constantly get fungused eggs, so I just tried Fungus Cure this morning-- immeidately after unplugging the heater on which they had chosen to lay the eggs and putting in a spare heater.
We'll see how it works. I have both MG and MB. If this doesn't work, next roll around, I'd love to know the answer to this, too!
(They have a PERFECTLY good slab of slate they've used like four times. But it's better than the sponge filter, which they were eyeing last night!)