My red tailed shark, Tom, was swimming around peacefully one day and when I looked at him the next day he was looking bad. Later that day he starting floating with the current upside down, sideways, forward, with the current. He was still breathing so I didn't know what to do. I never saw him eat but he had to have eaten because I had him for 6 months! He was getting weaker and weaker! I couldn't bear to see him suffer. He died later. I don't know how he got sick! PLEASE HELP because I want to get another one!