I have a GSM pair in my 210 that are suprisingly not very aggressive at all and I have been thinking about adding a pair of Rod's Onyx in their own nem on the other side of the tank. I know this is very risky and clown species do not mix except in large systems, so is a 210 a large enough system. The GSM pair rarely leaves their host gbta also. This is just a toss up idea so all opinions welcome. Thanks