So I purchased a sixline from the LFS about a month and a half ago. I know people are going to want pictures and I know it's easier with them but he moves to fast. Ever since I go him he has a white spot (larger than Ich but still very small) on his tail fin. It shows up like every other week. I'll look in the tank and he will have it then a week later it's gone. It's not sand. It looks like a white fungus. But I don't know. It doesn't seem to affect any other fish and seems to go away only to come back.