I often house several together and I've never seen a problem with them and the females will often present with eggs. I even have one that lives in a 12 gallon Aquapod with Waldo, my mantis and they seem to be doing fine together. When we first moved Waldo in, I thought I had gotten all the inverts out, but didn't realize we had two pom-poms in the tank and only removed one. About 3 weeks later we saw her running about with Waldo right with her. Crazy! They're both still in there months later...but I do NOT recommend housing them together as in most cases the mantis would kill all inverts in the tank.