Yellow Tang won't eat

[Mimbler1]

My 6 year old yellow tang (only fish in a 200 gal sps tank) hasn't eaten in over a day (unheard of for him). He has no other symptoms, looks interested in food, but won't eat anything but a flake or two. His stomach looks full, so I'm wondering if he has some sort of blockage. Do these symptoms sound familiar to anyone? He's been the only fish in the tank for over 6 years, so no one is stressing him, and water qualities are what you would expect for a reef tank:
ammonia zero
nitrate measure zero
phosphate measure zero
ph 8.15
temp 81 F
Ca 390
alk 8 dkh
thanks, Mike

 

[TerryB]

What are you feeding the fish? Do you store ALL foods including flake in the freezer? Do you soak the foods in vitamins and selcon? My first guess is an internal bacterial infection caused from eating tainted foods. Do not buy foods in portions that you cannot use up within a couple of months. I would start with a LARGE water change using well aged and aerated saltwater. How many varietys of food does the fish get? What are the foods it is getting?

Terry B

 

[Mimbler1]

TerryB,
The tang gets nori daily, plus a daily serving of osi flake food (I alternate between a couple of types). The flake has not been stored in the freezer, though. He also of course grazes all day on the rocks in the 200 gal reef. I currently change 15 percent of the water weekly.
thanks, Mike

 

[Mimbler1]

TerryB,
All's well with the tang today. Now that he is eating again, I threw away the old flake, and fed him some from a fresh can, as well as some nori soaked in Zoe. I've been in this hobby a long time, and never knew old flake could cause disease - I'm glad I learned it without killing a fish!
thanks, Mike

 

[TerryB]

Tainted foods are a major problem in this hobby. Storing everything in the freezer will help hold the nutritional value and prevent bacterial growth in the foods. You should be feeding the fish at least a half dozen different types of food. Glad to hear that your tang is doing better.

Terry B