That fine carpet of green on the rocks is a sign of a healthy eco system. That's what you need to see as a fish's buffet. There is no one standing above a stream or pond to feed you three times a day in the wild. fish need to find there own food and that carpet on the rocks is their dinner bell.LOL! These fish don't graze, they attack! The floating water lettuce and hyasinth is constantly on the move with one or more fish aggressively chomping on the roots. It's fortunate that those plants multiply so quickly. There is still a fine film of algae on the sides of the tank and they munch on that also. That was another reason that I thought they needed more food.