Up to this point Frank(my RTS) had been very easy going towards his zebra danio tankmates. However, I just watched one swim into his cave and holy ! It was like watching a lion chasing a gazelle! It's a good thing my RTS is still small or the danio would have been done. I'm gonna have to put a rush on getting my 55 set up. He is now bigger than them and realizes it. I'm okay with even aggression but in a few more months it won't be even anymore.