Nice to know about the firefish, I'll consider getting a few more later on then
One out of three people I have talked to that had Cherubs have said theirs were demons, like killing other fish aggressive. One was just normally aggressive (like my firefish towards my goby, nothing serious), and the other was a sweetheart... so I guess it just depends on the fish and the tank. The super aggressive one was in a 30 gallon and was already established, the others were in larger tanks and added after other fishes. I like them though, they're pretty fish (and the size is perfect).