Help! I went to the pet store today, and bought a betta. The lady said they had just been treated for fungus, cause one of them had it. The didn't have a light over the tank so i couldn't see this, but when i took my betta home, i saw that he has this white, almost powdery stuff on his face. What should i do. i know i can take him back, but i would prefer to fix him. what is wrong with my fish??? Please Help!