The smalllest wolf??... I think either the red hifin (Erythrinus sp. ) or Golden wolffish (Hoplerythrinus unitaeniatus). Not certain which one of them is tho??... but I think both these species hit the 8-12" range, max?!!
As for activity goes, I hear alot of people say that Red hi-fins are not very active, but my red wolf is actually very active! (more active than common wolves anyways). Mine will swim across the tank back and forth, begging for food. After it'd done eating, is when he will go to the bottom and lay almost motionless. During the dark hours of the night/early morning is when it is most active.
As for temperment, I hear alot of people say their temperment is mean and nasty. I mean, they are predatorial carnivorous fish, so naturally, they're going to hunt and eat other fish. Unless fed other optional foods; beefheart, shrimp, krill, pellets, frozen fish, or any other meaty foods. My red wolf tho... 'funny' is actually kind of a 'pantsy' or 'wuss'?!! Lol! It's been kept in a community tank with all kinds of different fish... aros, discus, tarpon, tig, red 'cudas, etc. Never ever touched any of them?!!
As for Golden wolffish (H. unitaeniatus)... they are the most active wolf sp. there is. Constantly swim around the tank everywhere!! Always begging for food. Top, mid, and bottom dwelling fish. And their temperment, I've kept a single speciman in a community tank before with lrg. fishes (aros, gars, stingrays, bichirs, etc.) and it did fine with them. Got along fine. But then another time, I kept a group of 3 in a tank by themselves... they were always fighting and nipping at each other all the time. Perhaps keeping them w/ other fishes in a comm. tank, may have balanced their aggression levels and maybe even made them group up together?!! Unfortunately, I never got to mix the 3 in a comm. tank, so I never got to find out whether it may have worked out or not?? All in all, all wolf species are great... sm. species, lrg. species, active species, boring species, active species... All wolffish... you just have to like and appreciate them for the fish that they are.

Whatever the reason may be, why so many people are drawn to them?... personality, mean looks & appearance, hunting/eating behavior, whatever?? One thing for sure, all wolffish are 'bad ass!!
