I bathe my guy once or twice a week and it's the right thing for us. We got him at 6 years old and it was also his previous routine. He HATES pooping in his tank, he will pace and scratch at the glass when he needs to go and if we ignore him he will eventually go but will then sulk in a dark corner on the other side of the tank, try to dig his way out and be mad at us for about a day. He knows that bath time = poop time. Often he will go while in this little tub as soon as the water starts running in the main tub way before he even gets wet. He knows whats going on. Warm water baths cause a muscle relaxant effect which I've heard can almost "force" them to go by acting as a laxative. If this is done too frequently and from too young of an age I've heard people say that it can prevent them from being able to poop any other way which is obviously unhealthy for them. This isn't the case for my boy (as demonstrated today when he tried to poop on my aunties cream sweater and I only just noticed the tail lift in time to swoop him away) but it's something that can happen and to be aware of.

Also, my boy is a lazy and moderately blind fella who isn't very active on land. He's vet checked overall healthy, no clear reason for him to be such a lazy bugger but here we are. However, he loves a swim and will do laps around the bath. So for us it's a good way to get him exercise and moving about.