Tang Breathing Too Fast?

[jck]

Can someone quantify what one would consider fast breathing? The reason I ask is that I *think* my Kole tang has been having some trouble breathing accompanied by some odd behavior where he's opening the gill on his left side very wide and holding it there. He seems better after changes I made last night, but now I've lost all perspective on what "normal breathing" would be. Any other recommendations on what might have gone wrong are welcome.

As far as tank information:

125 gallon with ~100 lbs live rock, 5" DSB, Ammonia 0, Nitrite 0, Nitrate ~2, Phosphate 1 (not sure where that came from), Ph 8.3, dKH 13, 100 gallon sump/refugium, Mag 12 and Mag 5 return pumps, ~800 gph from powerheads (~400 before last night).

Livestock includes the Kole Tang, Atlantic Blue Tang, L. Amboinensis Cleaner Shrimp, various snails (Cerith, Nerite, Limpet, Turbo), 4 Holothuria sp. cukes.

The system is fairly new (2 months) and was the result of moving from my old 100 gallon to a new tank with a DSB and a refugium. I've been fighting to get DSB populations going given I couldn't let it sit for a few weeks after seeding it. I've also been fighting diatoms and hair algae the last 2-3 weeks.

Any recommendations are sincerely appreciated. This tang was saved from an LFS and has been with me since I got back into aquariums 2 years ago.

[jck]

Okay...forget getting better. There's now erratic swimming and his color is fading off and on. The Atlantic Blue still seems fine. May not be anything left to do within a matter of hours. Please post or e-mail me if you have any ideas on helping him.

[billsreef]

I would suggest starting out by placing the tang in a Q tank. Based on the symptoms you are describing I would suspect a protozoan parasite simular in nature to amyloodinium or even amyloodinium itself. Therefore I would also suggest treating the fish with copper while in that Q tank. Also a 1 hr formalin bath before being placed in the Q tank might be a good idea.