I have a 40 gal tank. I started with 4 peppermints. I now only have 1. It is a peaceful tank so I very much doubt a fish killed them. I have read of peppermints attacking and eating each other, though have never had this issue in my 15 gal. My main question is....... If I add new peppermints is this guy likely to wipe them out also? Or should I get a cleaner shrimp instead?