Apollo is funny, he usually always goes in the bath, but if for some reason I haven't gotten around to giving him a bath yet or hes already had one (and didn't go) he will start glass dancing until i take him out and put him in the bath and he goes right away. He hates pooing in his cage.
I am trying to get thriller used to only poopin in water lol. I don't like having him poop in his tank.
I just put him in the bath every day and he didn't come out until he pooped, pretty soon he got the idea that water=bathroom. And now he hates pooing anywhere else. You can try doing that, the other thing i used to do is figure out when he normall went poo (morning, afternoon etc) and then give him a bath everday around that time....
Goooood luck lol.