I've seen my Blochiis spar with each other before (as well as try to spawn). and they can fight over territory some times, but are otherwise peaceful.. growth rate wise I've had my Blochiis a few months and the biggest one has grown probably 2 1/2 inches..
haha ok but why? theyre pretty fish yes but not really what i like, however if theyll have some sort of benefit in my tank, ie sifting through the sand, then ill consider them