The Damsel Trap is when you start your tank by getting damsels, and when you try to add new fish, the damsels attack the fish. This happened to me but I got out of it, one of my damsels, the worst one, suddenly died. He wreaked havoc among all of my fish. Once he died, I was able to add a bunch of new fish. Just remember to start your tank with some other hardy fish. Probably not damsels.