Clam in the wild yellow tangs form schools and swim and graze all day. So in a closed system it IMO
is very important to give them as much space as possible. They also seem to have a fast metabolism, and digest food very fast IME
. I keep 3 yellows in my 125, and they swim all day long back and forth. You could keep a tang in any size aquarium, but in my opinion the tank should at least be 6' for long term health, and a stress free environment. I have read this, been told this, and I have to agree with it. It dosen't mean you have to though.