Most herbivores poo a lot. Hebivores eat continually because plant matter cantains a low concentration of vitemins and nutrients compaired to meat. Also, herbivores have trouble digesting cellulose just like a carnivore does, even though herbivores do have clluslose motabolizing bacteria in their stomachs (which I am not even sure if surgeonfish do). This causes much of the plant matter to flow out undigested. This causes the animal to deficate a seemingly unreasonable amount.

My Convict tang drops bombs on an hourly basis. It comes with the territory of owning a tang. I have cut down on the waste factor by feeding it strickly pellet (fatty protein etc) and let it get most of it's plant matter from algae in the tank.

A healthy surgeonfish will graze all day. If you have a well established tank, , in my opinion, there is no need to suppliment it with "veggies" or other overpriced "tang food". Of course if your tang is larger you may need to.