O yea, I agree. You dont have ti bad. I had a teriitorial Clown fish, killed 3 fish in one night. TERRIBLE, lol. I got rid of him though, thank god. Umm, lawnmowers usually cant kill other fish. Their mouthes are designed to pick at algae, not bite other creatures. I think it would be the other way around. Damsels are terrible, they kill more fish just by constant pecking tahn any other. yer lawnmower did u a favor i suppose, but then again, id idnt know yer damsel. I'm pretty sure that he didnt kill it though, maybe the damsel didnt eat. Was it eating? Yes, get algae sheets, thats a good idea. Lawnmowers will cahse, but I'm very sure that they cannot kill.