White spots on Pectoral fins

[wetmanNY]

Spawning tubercles are common in goldfish and some, though not all, closely-related Cyprinids (q.v.). The raised bumps appear on the head, never on fin tissue.

Wartlike, slowly developing nodular growths on fins are individual cells that have been grossly enlarged by the virus Lymphocystis . Possibly the virus is slightly communicable, but it cannot be treated, even on a professional level.

Fish rarely trim their fins. A combination of bacteria and Saprolegnia are commonly responsible for such "fin rot." The funguslike Saprolegniales are actually water molds.

(If this were www.wikipedia.com you'd click on the highlighted links, eh...)

 

[Fishskin]

Wetman is correct, as usual. After "Googling" I absolutely agree that my fish has lymphocystis. As my tank is small, no one else is obviously infected, the condition has been visible for more than 2 months, and the disease may be self-limited; I will just observe. In my situation, I cannot really quarantine the "well" fish and do not see any good evidence that it would help now. Will keep water parameters in good shape and do regular water changes. Even though I did not make the diagnosis, my wart analogy was not far off, so , at least, I feel better professionally.