I give my fish lettuce, as a treat. They love it. I read broccoli is good as well as spinach. I haven't tried either of the latter. Funny to drop in a penny size peice of lettuce and watch my piggy clown 'drag' it around with him!! Also...frozen peas smashed up....read this in an aquarium magazine. They like the peas, but you have to take the shell off. I just do these as treats, not staples. I remove all uneaten within the 1/2 hour.