They put holes in my plants,lol, I feed them good meaty stuff too, (ramshorns,pond snails, market shrimp, frozen brine shrimp, the occassional earthworms and crickets(rinsed) that my kiddos find and want to watch them eat(although prolly not the best because of potential lawn chemicals)BUT the earthworms and crickets haven't hurt them yet, and boy do they love'em! Anywho, if at any pet store or fish store you see a tank that has had gsp's in a tank for a while with plants, you will see little, almost perfectly round holes in the plants. Yeah, the plants I had in their tank got hole punched, too,lol, oh yeah, however, they most likely won't eat java moss, but you never know, they seem to like to taste all of mine.(java fern)and leafy things