Don’t confuse algae with mould.
Algae start appearing late into incubation, only because I use a light bulb as a heat source and clear containers.
Mould is no good, when an egg starts moulding I take it out pronto, this mean the egg is week and has no defence to bacteria.
Be advise 100% breeders will advise you to incubate eggs in the dark.
Rgds