I have a few Tiger Barbs and one of them has this slight gerrn moss looking stuff on his stripes. it kind of looks like glitter. He has an appetite and swims around. But, when the other tiger barbs chase him, he kind of swims fast at an angle. When he swims at a normal pace, he doesn't do that. Nitrate is very low. Ammonia is .1, nitrite is 0. I'm going to do a PWC now. WHAT IS THIS STUFF?