my yellow tang itching against glass causeing red rash
hi this is my first time posting on this web site. i have had my yellow tang for about 8 months and all of a sudden he has been rubbing both sides of his back end against the glass turning it into like a red rash. he only does this in one spot and no were else in the tank. i have had the tank for about 2 years i have a clown, six line wrasse, sunrise dottyback a cleaner shrimp 5 turbo snails 4 hermit crabs and about 8 pieces of coral. my water is almost perfect besides my calcium ph 8.2, ammonia 0,nitrite 0 my calcium is only about 300ppm. my tank siz e is a 30 gallon and i have about 25 pounds of live rock and two big caves he can go in, and i feed him mysin shrimp twice a day and a piece of seaweed twice a day. i have a qt tank but had bad luck with it (only one out of four fish made it out alive) what do u think i should do, and is wrong?