[why are you trying to catch the CBS, if you do not mind me asking?
whenever i need to catch anything in my tank, i do it at night with a real dim flashlight and surprise them. but, since your CBS is probably active at night i would say use some type of frozen food for fish and bait him to come out and attempt to net him or take out the live rock he is on.
My coral banded pretty much eats out of my hand as does my cleaner shrimp.
not sure if this is going to help, but just my opinion.
good luck]