My Goldfish has developed what looks like a mole. It seems totally fine otherwise. It also has two darker, more faded, spots on its tail fin. Both have suddenly appeared and have been there for months now. What are they? Probably not ammonia poisoning because the spots have not worsened or lessened over these past months and ammonia levels are fine. The “mole” near its dorsal fin also seem to have very sharp outlines which would not be the case with ammonia burns. A probably unrelated note: last time when I did a water change tiny bubbles of air seemed to attach themselves to a very thin and translucent string attached to the goldfish body. It may have been nothing and i cannot see it now. As a precaution I have dosed him with ESHA 2000. That did nothing for the dark spots. Any ideas? A natural change in color or a sign of some sort of disease ?? Thanks in advance for your ideas, folks.