seen 'em up to 18" , contrary to their looks they're not an aggresive predetory fish in most peoples view of the deffinition. They are essentially filter type feeders who comb the bottom like most gobies do, hence the other common name. and pick up fine meaty foods. always had them at work, deffinately brackish. frozen bloodworms and brine shrimp where their staple and a HQ marine flake was offered as well. which they usually took to pretty easy. sand bottom or fine gravel seemed to be the best with them for substrate, non-aggresive tankmates. and ideally 55 gal + for a home. personally i found them pretty boreing, so never took one home. they do look interesting and would prolly eat small fish like molly fry if given the chance, but i'm not sure.
I hadn't thought that he would be so cool, but he is (to me). I hope this helped a bit 