Hi my 8 month old red oscar, having about 10 white spot on his head, first its was very tiny white, then stop feed it with goldfish, I feed him with formular, today I saw the spot getting bigger, I change water yesterday and I change again today, it current on 20 gallon tank, next month or so I will afford a 50 gallon tanks, but now im keep change 5 gallon water every 2 day, and only feed with the formular, and I want to ask what kind of medicine I can put in to treat the spot ? I live near by pet mart. thanks