Do Cole tangs fail to thrive?

[debby]

I have a cole tang and although he appears to eat ALOT, he still looks a bit thin - any suggestions??

 

[TheTodd]

What are you feeding it? How often? What size tank?

 

[Gregcoyote]

Kole tangs need a surprising amount of vegetable matter to stay fat. I keep a almost constant supply of romain lettuce and nori sheets clipped into the tank. The Kole is a constant grazer, as most surgeonfish are.
Another reason they need a tank that is large enough and has an aggressive filtration system to handle the large amount of poop surgeonfish create. Vegetable matter diets and short digestive systems can make a mess quickly.