I've been keeping three greater sirens outside all spring and summer, they're in a large 5 x 3' plastic container and are fat and healthy. Now winter is approaching i was wondering what sort of cold temps they can take. I keep my axolotls outside in a similar tank all year round and they are fine, the water freezes over and temps can get down to minus three or lower. It was pretty cold when i put them in the tank but no where near as cold as it is in january so any advice would be greatly welcomed.