The Goby you are talking about often has the common name "Marbled Goby" I'm not sure of the scientific name of them, but I can find out if you'd like. They are very interesting, but HORRIBLE for a community tank, first of all they can eat a fish almost half thier own size, and although they spend most of their time waiting for prey at the bottom of a tank, will often move at pretty incredible rates if startled. I'd say unless it is a showcase, or pet fish for yourself, stay away from them! There are plenty of other, more peace-loving gobies that suit a community quite well. They grow to about 6 inches in size, and come from the Malay Penninsula. Like most gobies are pretty fussy about having live food. They are very hardy fish as well, and can take nearly any tempature and pH range, (within reason)