Well the ideal amount would be at least once a week,when they are shedding every few days is nice b/c it helps them shed better, but they can go a long time without one,but i wouldn't let it go past 2 weeks,when i put zilla in the
bath he puffs up,sits in the water for about 10 minutes then he'll poop and swim around for a bit,it looks like he's clawing at the side of the
bath tub to get out but he's completely safe and it's a good workout for his arms so i just let him swim,i usely put my hand in the water palm up so he can swim somewhere for a break if he wants,a big rock/object for them to lie on works well too, just make sure your always watching them and if they seem like there freaking out take them out for a bit and cuddle them,you can put them in after that too make them feel like the
bath is safe too