the red eared slider forum I'm a member of; states that a male can live in a 55, as long as there is enough filtration. Males max out at 5-7 inches. FEMALES get the size of a dinner plate at 12-13. That means 55-80 gal minimum for a male, or 120-130 minimum for a female. Some keep their turtles in stock tanks (the ones used for livestock) or waterland tubs. To expand the swimming space, some keepers build a platform that sits on TOP of the tank, like a penthouse. That leaves the whole aquarium for swimming, and still gives them basking areas. That's what I'm planning to do for my turtles in the near future.
