I just got a 29 gal biocube (with the only fish being 2 yellowtail damselfish) a couple of days ago from a friend who could no longer care for the tank. It has been established for years in his house and I moved it to my house 3 days ago without adding anything new. On the second night, one of the fish started nipping at the other so badly he ended up with torn fins and died by the next morning after a night of breathing rapidly and not swimming well. Now I have noticed that my remaining fish has a few white spots on the top of his head but is showing no other symptoms and seems fine. My first thought is ich but I am new to the hobby and would appreciate advice as to what I should do!