Have had mine for about 8 months now. They will stay on the bottom of the tank, not great swimmers. Have arm like pectoral fins in which they crawl along the bottom. Probably are happy in areas of low water flow, although my tank as pretty heavy flow and he gets along just fine. Eats anything meaty (Brine Shrimp, Myssis, etc.).
Does not bother any other fish, no one seems to even notice him in my tank other than one other blenny, and they are fine together. Mine has no fear of, me, my hand, or anything i put in the tank. I could grab him with my hands or catch him anytime I want, whenever I am cleaning the tank he is usually right in the way, and will follow me around the tank getting in the way. They have a nice emerald color, but it can fade if the tank is washed out with white sand / light background etc.