My dad has about 18 of them.
All different sizes. Some of them are as old as he are (50+)
He feeds them ox heart and snails from the garden.
He also goes to the big bins in the vege sections at supermarkets and takes the lettuce leaves people reject. They love it.
Quite cool to have. My dad built about 3 big ponds for them. one is a little round about for the driveway at the house.
They also bite like a bitch and wont let go easily.