Oops I forgot.
On my tub, I carefully cut out the bottom, and it was supported laterally with branches, to keep its shape. Then i slipped that tub,, with all the fixings into another of the same type. So to clean the bottom, I just removed the inner tub, with all the fixings and the babies and slipped it into a new clean one.
I would spray things first, to try to wash anything into the bottom to remove it.
I've always loved to build and design. I get as much enjoyment from that as I do the critters.