Ace,
i didn't know you have a bluefin...what temp are you keeping your tank at? how long have you had it?
we've been running our bluefin tank at 66*F, and have had our specimen a bit over 2 mos. it's a gorgeous fish...one of my faves. it is stick-trained, but isn't a super aggressive feeder. it will also take mysis and BS+ from the water column. if nobody is within sight, it rests on the substrate, but if it sees us, it's up and begging.
IMHO, i dunno how long i'd keep it with a volitans tho...they don't get very large. however, if they grow up together, they might be OK.