North American aquatic turtles will become relatively torpid as temperatures fall below 15oC, and enter hibernation below 10oC, and European turtles respond in the same way. To overwinter, maintain temperatures above 20oC at all times.
Tropical & temperate aquatic turtles
Most of these turtles are well suited to a vivarium environment, although in some cases outdoor accommodation can be utilised during the warm summer months. Because these are all relatively small species, it is possible to base the vivarium around standard tropical fish tanks - however, only large ones are usually suitable. The minimum I would normally consider satisfactory for a fully grown adult pair of Red-eared sliders for example is 2m (6 feet) long x 500mm (24 inches) wide. This should be 50/50 to 75/25 land and water in most cases. Other housing options that offer superior qualities to glass tanks are available, however. See the links at the end of this article. In particular, the surface-mount pond concept is vastly superior.