Knowing what kind of habitat to provide your turtle involves knowing where he comes from and how to mimic his natural environment.
Land Turtles and Tortoises
Box Turtle Habitats
For land turtles such as the ornate box turtle, provide a 30- to 40-gallon aquarium as a habitat for small groups of turtles. Fill the bottom with at least 4 inches of sand and soil substrate in which the turtles can burrow. Place a sturdy water dish in the substrate deep enough for the turtles to soak their shells but not deep enough to drown. These turtles will munch on live plants, so use only plants that are nontoxic to box turtles. They also need access to UVB lighting. Install full-spectrum reptile lighting over the entirety of the enclosure and keep this on for 10 to 12 hours per day. On one side of the tank, use a heat lamp that provides basking temperatures at the surface of 90 degrees Fahrenheit. Allow the other side to be warmed by the ambient heat of this fixture -- 75 degrees is sufficient. At night, turn off these lights and let the tank drop to room temperature.
Keep the red-footed tortoise outdoors during the late spring, summer and early autumn months in temperate climates. Construct enclosure walls 16 inches above ground and 6 inches deep to prevent climbing and digging, respectively. Ensure that both sunny and shady spots are available to the tortoise. Choose a location that will not flood in inclement weather and ensure all grasses and plants in the area are nontoxic and have not been treated with pesticides. Provide a water dish large enough to soak in but not large enough for the turtle to drown.
In winter or extreme weather, bring the tortoise inside and use a plastic sweater box or similar container with opaque sides. Fill the box with sand and soil substrate. Provide UVB lighting and a heat lamp that creates a basking area in the 90-degree range. Room temperature at night is sufficient.
While box turtles and tortoises are landlubbers, many other types of turtles need constant access to water to thrive. The red-eared slider and painted turtle, for instance, need both swimming and basking areas. To construct a habitat for these turtles, choose a tank or pond relative to the size and number of turtles you have. For every inch of turtle shell, you will need 10 gallons of water space. A 5-inch turtle, therefore, needs 50 gallons of water in which to swim.
Fill a suitably large aquarium with dechlorinated water and install a basking dock to the side of the tank at the water line that gives your turtles a place to climb out of the water and rest. Use a water heater with a heater guard to bring the water temperature to 75 to 85 degrees Fahrenheit. Install a basking light and full-spectrum reptile lighting above the dock that provide UVB lighting and temperatures of 85 to 90 degrees. Outfit the aquarium with a filter to keep the water clean and aerated -- poor water quality can lead to shell, skin and ear infections.
Some aquatic species like the snapping turtle are best kept outdoors. If you choose to keep your aquatic turtle outdoors, be sure to provide ample basking space and a pond filter to keep the water clean. Make sure that all sides of the enclosure are secure to prevent both climbing and digging. Ensure that the turtle has access to both shade and sun and avoid community housing with animals that the snapper might eat.
If you wish to breed your turtles, consider providing conditions that induce brumation -- the reptile form of hibernation. This generally involves a drop in temperature, a reduction in feeding, and shortened lighting hours. Storing your turtle's habitat in the garage during the winter works for many species. Contact a herpetologist or veterinarian for guidance on how to brumate your particular species of turtle.