I'm more into corals than fish...
My experience has been.
Put the BCB with the RG in a 20 G. The RG starts with the posturing but the BCB would "win". Still no real dmg... often.
My 75g reef has a LMB and a Fire Fish. I moved the RG and BCB to the reef.
First time I see the RG after the switch he has no tail. But he gets his own little hole and small area... months later I switch all the rocks around and the next morning he is missing all the fins... Now, though the RG and LMB have never been seen interacting... I suppose it could have been him or some other force... but I have atributed the abuse to the LMB.
The BCB and the FF and the RG are all around the same mass; the LMB is at least 50% larger than the rest. The BCB often attacks the LMB and wins, but to no dmg. The LMB clearly does not fear the BCB ... but he doesn't fight back much either.
Both the LMB and BCB are extreamly cool in my book. Wait till you see the BCB sticking his butt in every hole to find the right home.
I am not a clown fan, but I doubt that the BCB will have much luck out agressing them if they (it) has its territory already.
Once again I am no fish expert, this is just my one singular experience with this fish.
edit:
The only coral (and I have all types) that have been nipped (and only by the LMB) was one with hair algea.
edit, edit:
I am not sure that the clown and bleeny really share the same feeding habbits. FF are real wimps IME. but the FF is a column feeder.
The RG and BCB have almost the same feeding habbits (competition (sp)). And though the BCB eats some bits of algea from time to time, I doubt he would even bother the LMB except for the fact that the LMB simply does not care about territory at all!!! The pig head! Infact, he doesn't care that I pet him evertime its ric feeding time.