I understand wanting to put two species together, I reeeeally do, but it's just not a good idea in this case, the species are too different. Can you put up a picture of their cage? I'd say that that size is way way way too big for a BP, but who knows, maybe you have it set up really well? I understand wanting to give them a big beautiful cage. Maybe put the GTP in the cage and move the ball to a smaller one?