anna there is always a possibility of a mantis shrimp with the rock i have but i've gotten probably around 2 tons of this rock and have only ever seen two mantis shrimp. i inspect each rock and if the two times i've found a mantis i was fortunate to catch them. other than that the only bad stuff i've seen come on the rocks is the occasional aptasia. the holding tank i have this rock in has a ton of peppermint shrimp so the aptasia doesn't last long lol. im not to far from BG if you ever want to come check them out.