I had some fish in my tank, and they all died from ich or velvet. left the aquarium empty for 75 days, ran the fish through blue life fast quarantine. all the fish (two Ocelaris and a royal Grama look nice) today a week later, I see royal g rubbing against the sand, and it can look like the fish has a parasite or something on it. How is that possible, if the fish die again I think I'll quit, I can't take another 3 months with no fish.