One of the main types of fungal diseases in farmed salmonid fish is saprolegniasis, caused by species in the genus Saprolegnia. It causes considerable economic problems in the fish farming industry infecting both fish and fish eggs.
this is becoming a big problem as legally there are less and less treatments available. Previously malachite green could be used but this has a serious environmental impact and is no longer allowed for use in food fish species. There are other antifungals that are good but as with any medicated treatments the important thing is to follow a therapeutic regime and then keep organic waste matter to a minimum.
We use a product called "Phyzese", but I have to look into the working agents and proper product name... In pond farming they use "kaliumpergmanat", but I dont know if it would be allowed to use?