Thanks, all. I checked out Nano-Reef, and the only fish that is "recommended" (I say that loosely- to be exact, it's the only fish with a minimum tank size smaller than my 6-gallon) is a firefish (although other sites recommend a larger volume for that species). I was surprised to see that even a clown goby needs at least 10 gallons.
I guess I'll just have to keep my eyes open for little runt-sized versions of some of these fish that look like they might be stunted.
