In the case of goldfish pond fungus, the most effective treatment is malachite green. It is recommended that one treat an entire pond before trying to treat the infected fish separately.Continue Reading
"Pond fungus" is a bit of a misnomer, as the fungus grows literally on the fish themselves. One of the most common fish diseases is saprolegniosis. It appears as white, green, brown or gray cotton-like tufts that can protrude from any external body part of the goldfish. Saprolegniosis is primarily caused by one of three aquatic fungi: Saprolegnia spp., Achlya spp. or Dictyuchus spp. Although they each differ slightly from each other, their characteristics are so similar that it is advisable to look at them as one singular invader during treatment.
If it is not possible to treat the all fish together, separate the infected fish, and place them in a second container with matching pH and temperature and an airstone aerator. Let each fish soak for an hour in a 5-parts-per-million concentration of malachite green once a day for a week.Learn more about Veterinary Health