The Royal Gramma I just had to evict was aggressive toward anything that went near a rock. Did not matter which rock. This was in a Biocube which is fairly tall instead of long which I am sure contributed to the problem. Attacked my watchman goby so often that it stayed under a rock and did not come out. Dive bombed my peppermint shrimp often, bumped or threw crabs and cerith snails off of rocks, often chased my Clown around. I researched and it seemed they are hit or miss, either real chill or REAL not chill. You can find some other threads here about it if you search, one is showing up right now for me in the "Similar threads".