Actually, I think it's not alive. I just googled for it, and it appears to be just a really poorly thought out souvenir/gag gift kind of thing. It's a dead baby sand shark that may or may not have actually made it to a live birth, preserved in formaldehyde.
I got a 7 in. Jack Dempsey in a 40 gallon tank by himself. I know my tank is on the smaller side for a JD but he is doing fine. I would never add another fish to his tank. I cant stand when people buy alot of fish with very little knowledge of their standard living conditions