Symptoms:

• Darting around tank or rubbing against glass or ornaments. I mistook this for chasing a reflection.
• Small black dots on fish

What is it?

Black spot disease is actually the larvae of a digenetic fluke embedded in the skin of the fish. These parasites have a very complicated life cycle that starts with a mollusk, moves to a fish, and then to a bird.

How did it get there?

Black spot disease is common among fish living in ponds or lakes. It normally occurs after having added new fish. Be sure to keep new fish quarantined for a week or two before adding to an existing tank.

Treatment

Since the black spot disease has such a complicated life cycle, no real treatment is necessary. The cysts produced are relatively harmless to the fish, unless the fish is a highly contaminated juvenile which may result in death if not treated. There are a few medications out there for Fluke infestations.

Prevention

• Make sure that you quarantine all new fish for a week or two before adding to a community tank.