Are you certain its not Slime Disease
This disease is also caused by protozoa e.g. Chilodonella, Ichthyobodo (Costia), Trichodina and Brooklynella species, and Trematodes (flukes) e.g. Gyrodactylus and Dactylogyrus species.
These parasites spend the whole of their life cycle on the fish, although infective young parasites may be released into the water to spread to new hosts. The parasites live on the skin and gill surface, eating gill and skin tissue debris. If their numbers increase rapidly, they may irritate the skin and gills, causing excessive mucus production and usually killing the fish by smothering the gills and hence suffocation.
Slime Disease Treatment
The correct treatment (such as Interpet's Anti Slime and Velvet No.7) quickly and effectively eradicates gill and skin parasites and removes the mucus build up, therefore aiding the fish's respiration.