Well, I once thought my 40g was devoid of mantis shrimp. After a feeding of live brine shrimp I realized that there actually was a mantis in my tank, in fact, there were two. While cleaning my tank today I reached in to straighten a piece of rock the way I wanted it. I guess one of the mantis wanted it the way it was so he nailed my finger. It hurts bad!!! I am a one handed typist for a couple of days. I tried getting the little ******* but he got away. I'm lucky, it looks like a big needle ***** that teared a bit. It's a good thing Philippine are little guys, get to a max of about 4".