This affects Koi more than it does goldfish. Basically this is a viral infection which causes a whitish or pinkish waxy film to develop over the fish’s skin and fins. The usual pattern is that it appears, gets worse and then disappears.

We have no idea what triggers it or what eventually happens. However, it does not appear to be contagious, as far as anyone can tell. Of course, you probably should separate out the infected fish until you can figure out what it is, or until the film goes away. It will usually go away within seven to ten days, with a salt treatment or without one. It’s more annoying than anything else, since it does not kill the fish. However, there is no known cure either.

Related posts:

1. The Basics of Pet Goldfish: Fish Lice (highly contagious)

2. The Basics of Pet Goldfish: Leeches (highly contagious)

3. The Basics of Pet Goldfish: Diseases of the Goldfish

4. The Basics of Pet Goldfish: Swim Bladder Problems (not contagious)

5. The Basics of Pet Goldfish: The Old-fashioned Salt Bath

6. The Basics of Pet Goldfish: Emergency Cleaning

7. The Basics of Pet Goldfish: Spawning and Breeding

8. The Basics of Pet Goldfish: Velet and Fungus

9. The Basics of Pet Goldfish: Pond Keeping

10. The Basics of Pet Goldfish: Fin Congestion