I have 20 ghost shrimp. They are a trip. Anything is right. Debris, leftover food, fresh foods, pellets/flakes/wafers/live brine shrimp, you name it it eats it. I can't believe I actually stuck these things into butter. It makes me hate to eat shrimp again :) The more the better, these are great little workers. They will eat at the surface, on the plants, on the bottom. Timid little guys but cleans your tank so very well. I also have Olive Nerite Snails, between the shrimp and snails, uneaten foods are not waste.