Best way to keep them is in a sandy substrate. Its awesome to watch them sift through it all day long lookin for food. There are two species available commonly, jurupari, which is really actually harder to find, and leucosticta. Leucosticta actually has more spanglin on its face, makin it relatively easy to distiguish if you know what to look for. Both are great fish, definately a great choice!!
I've kept mine with Red Terrors, Viejas, Uaru, Crenicichla, and even a Red Tailed Giant Gourami...haha. They are pretty spunky little guys, but you do have to watch that they don't get beat on too bad. They are indeed slow growers..i think mine grew an inch in about two months...if that.
BTW...they are no longer Geophagus any more, they have been moved to Satanoperca...annoying how they keep changin the genus.