Help!!!

[tang lover]

OK i have a green chromis. and yesterday i noticed that there was a little scratch on his side. and then this morning i noticed that the scratch was taking up most of his left side.
i have
1 black perecula
1 blue tang
1 sailfin tang
1 yellow tang
2 zebra gobies
1 red head goby
Help Please.

 

[hatessushi]

What size tank is it? Is it a scratch or a slice like from a blade. The tangs have a razor sharp fin on the bottom they use for protection. do the fish chase each other around a lot? It sounds like it may be aggression from somewhere.

 

[bill109]

its a 80 gallon (i looked at your profile)
i say i almost know.. your tangs are probally starting to fight in tht small of a tank for one tang it is reccomneded a 75 and for 3 at least a 125. you need to have 1 or 3 or more as you prolly know but they MAY be starting to stress and taking it out on others .. they are a territorial fish
keep an eye on them and if they chase anyone take them out take out the sailfin and blue so the only one left is yellow. blu needs a 125 and the sailfin as well