Fish Lice and Your Goldfish
Fish lice (aka branchiura) are an external goldfish parasite large enough to be seen with the naked eye (they can reach up to 5mm). They are an eight-legged crustacean, greenish in co lour, and they use their legs to swim until they get a hold on a goldfish.
Apart from being visible, the goldfish will display classic external parasite infection behavior such as rubbing against objects in the tank or pond.
What is the problem with fish lice?
They feed off your goldfish by inserting a kind of straw into your fish. This can be the cause of bacterial infections.
What is the treatment for fish lice?
Fish lice can be removed from the goldfish with tweezers, or medication (organophosphate) can be obtained from a pet shop.