mine is about 12" and has eatin a small psuedo, a cleaner shrimp, a pistol shrimp, yellow assessor and a small goby. All small critters that im sure presented themselves close enough to the eel to be eatin so i learned my lesson, no more tiny fish in that tank. They won't really actively hunt other fish or shrimp, but if they r waiting and the fish swim close enough to the eel they will grab it. Safest bet is just dont keep fish small enough to fit in its mouth and you wont have any problems. Anything bigger than small psuedos and gobies will be fine.