Goldfish Has Black Lips And Fins. If your goldfish starts to develop dark black spots in various areas of his fins, tail, or scales, then this is an obvious way to see that he has black smudge (black spot). Test for ammonia, if present, perform this life saving water change.
If your goldfish starts to develop dark black spots in various areas of his fins, tail, or scales, then this is an obvious way to see that he has black smudge (black spot). You may notice that your goldfish has a small amount of black at the edge of its fins. Rarely, the black spot could be a disease passed on by snails if the snail has been exposed to bird droppings (as in an outside pond) and is still in the first generation.