On top of that, for a mantis shrimp there is no such thing as enough food. If something is in the tank that even remotely bothers it, it'll go after it, no matter if it's fed well enough. Hell, if YOU stand outside the tank too long the mantis will try to get through the tank and get you. And it can probably take you down, too. And as to the lionfish being venomous, I've seen my mantis take down a blue ring oct too, and it felt just fine and dandy later. You can't stop these little buggers.