sick yellow tang

[mtfish]

I have a 75 gallon fowlr tank. Have one tomato clown, one javanese damsel, one blue damsel, one cardinal fish and one yellow tang. Also have one long-spined sea urchin. Tank has been running for about 8 months. Yellow tang was last fish added about 3 months ago. Today the tang is acting lethargic and has a little poop hanging out that he is not expelling. All other animals are acting normal. Tang was acting normal yesterday. I did notice the water temp was about 2 degrees lower than normal so put a heater in the sump. Ammonia read 0.25 (which seems strange), nitrite = 0, nitrate = 15. In the process of doing a water exchange to get parameters better. Tang is still slowly swimming but did not feed today. Any suggestions?
Thanks

 

[melosu58]

Ok what are your water test results today. Ammonia amounts in any amount is lethal in a SW tank. Any other observations about him.

 

[mtfish]

bad news

Thanks for the reply. Ammonia reading is inbetween 0 and 0.25. Nitrite still 0. Nitrate went up to 20. But I lost the battle and have lost the tang. I looks like it just starved to death, but had been eating well 2 days ago. Before I go forward with more fish to stock, I need to get a handle on filtration. When I started the tank I had a canister filter, but am trying to go strictly with live rock and sump system. Until I get water chemistry stable, I am at a stand still. Again thanks for the reply.