Sure?
They eat the rest of the digestion of the food your fish eat. Not bad, but enough?
Do you even trust in the quality of the food you give to your fish?
I don't. As I don't trust the quality of the ingredients used and the manufacture and preservation techniques used to prepare nor my fish food not mi dogs (and I try to bring them the best possible.)
Not saying it's bad either, but wouldn't trust only on it when in our hobbie now there are very good reef foods.
Pretty sure, yes! As to the rest .... ok ....