I've had CPOs on several different occasions and they've always been calm and serene. I bought two for my 10 gallon a few months ago and one of them has all of a sudden has gone Charles Manson crazy. It killed its neighbor CPO, five yellow Neos, two Amanos, and an Otocinclus. This has all happened in the last week. The little ******* has been banished to its own tank.