I currently have 2 Eastern long-neck turtles in a 3 foot tank. They're only about 5cm roughly at the moment. Just wondering how long they can stay in this size tank for and when I do upgrade my tank in the future, what size would it have to be to house them when they're adults? Just asking because I don't want to buy 3 different sized tanks. The next tank I buy will be the last tank hopefully. Cheers, Daniel.