Second NEVER EVER put a snapper with any other turtle unless they are 2 adult snappers of oposite sex in a huge outdoor enclosure and your in the way of becoming a snapper breeder...or babys by a few weeks after hatching. Snappers inflict horrible desfigurating wounds in other turtles, all it takes in bad mood and also snapper are naturally predaceous thoards other turtles. DONT do it. As for puting the asian boxy with a yellow belly....really it depends, is the boxy male or female, what size its the enclosure, what species its the boxy. If I had to say a simple awnser I would say no but it gets trickier then that. However if you are indeed limited in space, oh yea defenetly no.