Purple tang is changing color

[sparta]

How do I fix this problem

[bribo12]

What do you mean by changing color? What color is it changing? Pics?

[sparta]

this is what he looks like

[bribo12]

Looks like a bad case of hlle.head and lateral line erosion. Can be from poor diet, stress or a combination. What do you feed it? Size tank? Tankmates?

[sparta]

I feed it seaweed and he is in a tank with a sailfin tang. And a lionfish and a queen angel

[sparta]

I have them in a 55 gallon tank. Because my other tank went bad and I have to change my water

[Sniperhank]

Such a small tank isn't big enough for one of the fish that you listed, let along all of them. Due to their size I'm sure that the nitrates are rising along with aggression for territory...not to mention not being able to keep two similar looking tangs in a 6 ft long tank without aggression issues. You're lucky it lived to this point, but with the current condition I wouldn't expect it to make it much longer.

[bribo12]

I agree with hank. Even if you can nurse it back to health it will most likely have permanent scarring. Can you setup a hospital tank or find a more suitable tank for the other fish?