I think you have that backwards. Gibbus reach only about 6-7 inches and charax can get up to about a foot in length depending on which species. I think George had some 10"ers for sale not long ago. As far as tankmates for a Hoplias, I dont think you'll have much luck, but that's depending on tank size. Mala's rarely get to the 2 foot mark in an aquarium. It also depends on which varient you have. While some can reach around the 20" mark (like the Goias strain) most usually top out at around 16". Most people that have wolves over 18" usually buy them at that size. Either way, good luck bro.