i would agree with Florida gar, this also shows the slightly upturned snout that we are seeing with these 'farm-raised' floridas coming in. keep an eye on that, and make sure he doesn't bang his head against the glass.
also keep an eye out for fishes bullying it or stressing it out; richard (polypterus) and myself have found that moving a small gar to quarters that large too early will often result (or highly increase the probability of) a broken back.
if you have a smaller tank (like a 50g breeder) i would move him to that and grow him out a bit. sounds counterintuitive, but we have found this works best with small gars.--
--solomon