sick comet

[comet_nut]

This has got to be the oddest disease that I have seen in my comet grouper. He was hidsing for about 5 days and then I saw him yesterday and shocked. Between his eyes and the top fin he has lost all his scales and it looks as if my hermit crabs had been eating away at where his brain would have been. The area is covered in a whitish film over what is left of his scales. I have treated the tank with primafix and despite as though he looks like half his brain is missing he is stillactive and eating. None of the other fish are showing any symptoms, although my damsel is swimming somewhat irratically (not unusal for this fish though). Any ideas?
The parametres are all normal ammonia .25 nitrite 0 and nitrate 20 ph 8.3. His tankmates are damsel, lawnmower blennie, sixline, flame hawk and a blue chin trigger. They have all been together for about 6 months and no recent changes of anything else.
This fish is excepionally hardy (lived through two ich bouts and never got a symptom) and hate to see it suffer.

 

[beth]

.25 ammonia is not normal and it is not something to rest easy about either. It can be lethal to fish.
Could it be that your grouper is the subject of abuse from another fish?

 

[comet_nut]

The ammonia has been at .25 for the last six months. I really dont think the tank is overloaded, its a 200G tank with copious amounts of live rock, so Im confused about why its there, but it hasn't seem to make any difference to my fish.
I don't think he is subject to abuse. He is king of the tank and the others know it. The only possibel fish that could even cause that level of damage os my blue chin trigger and shes so placid its frightening!
It was the whitish film that had me thinking it was some sort of fungal infection