I have a 10 year old Gouami that has developed a black spot on his head that grows a black stringy hair like growth for about 4 days then it's gone. The spot is about 1mm dia. and the growth gets to about 2mm long. All his tank mates are fine. He started this about 2 months ago and only today he has been hiding, coming out only to eat. I do a 25% water change every week and the chemistry is good.

