I have noticed that there are a few white string looking thing embedded on the sides of the fish. The length is barley 1/8 to 1/4 inches. They don't seem to bother the fish and I see one once in a while. Are these some sort of parasite? If so, what should I use to treat the tank? I have seen these on three of my discus within the last three or 4 weeks. They seem to disappear after about 3 to 4 days. Any help would be greatly appreciated.