I'm building a large pond this spring, around 12'x10'x5' with a 2' wide by 2' deep shelf on 2 sides. There will be about 10 koi, a bunch of longear sunfish and some snails and frogs. What kind of turtle can live in there year round. I like softshells but I dont know much about them. I can bring them inside during the winter if I have to.