Don't know what type of gobi it is. But its only 1 1/2 inch, and hasn't changed in over a year that I've had him. All I know is he came with some live rock. He's awesome cause he's what I call my ninja fish. He disappears till you feed them and he darts out from the rocks and right back in. This is the clearest pick I've been able to get since I've had it.
Below is a shot of my mystery wrasse who is colorful, docile, reef-safe and only about 2". I believe their max size is 2-3" so that'd be perfect for a nano of 30 gal+. I feed mine Arcti-pods, mysis and cyclop-eeze and seems to love it! Gets along nicely with my only other fish; an ocellaris clownfish. It's fun watching him swoop in and out of the rock work!