Although turtles can be housed in suitable equipped outdoor enclosures, indoor ones will be addressed here.
Indoor enclosures must be at least 36" x 12", or about the size of a shallow 40-gallon tank. Wood enclosures of the same dimensions and high enough so the turtle can't climb out may be built. The insides of such wooden enclosures must be waterproofed with several coats of epoxy or non-toxic based polyurethane, and left to cure for several weeks.
Create the land area using 2 to 3 inches of good quality plain sterile potting soil slightly moistened. Do not use backyard dirt or soil from a garden, and there should be no perlite or vermiculite mixed into the soil. Mix the soil with finely shredded orchid bark. You may also use plain fir or orchid bark, or deep drifts of alfalfa. Do not use coarse substrates such as sand, gravel or rock, which can scratch the shell, opening the way to bacterial infections. Your turtle requires a shelter or hide box filled with additional substrate material, or drifts of fresh alfalfa hay, in which to burrow. This can be made out of wood, cork bark slabs or even a cardboard box with a doorway cut into it.
A water area is required and can be provided by putting in the tank a dish or pan that is large enough for your turtle to lay in and shallow enough for it to easily climb in and out of. If a kitty litter pan is used, it must be recessed into the substrate, and a ramp provided to get in and out. The water must be changed frequently to keep it scrupulously clean.
You will need two heat sources: a heating pad under the tank and an incandescent or spot light over or to one the side of the tank. If using a wooden tank, the heating pad can be placed inside under the substrate. A large hot rock may be used only if it is set into the soil with a pie plate or other heat diffuser is placed over it, bringing it up to just below the surface of the soil; don't expect the turtle to just climb on top of the bare rock. Note that even with the diffuser, this will not provide enough heat over the broad area that is provided by a heating pad. The turtle may also dislodge the diffuser as it burrows around, requiring you to constantly "replant" it.) The heating pad (or hot rock) must be kept on all the time or as needed to maintain the proper temperatures.
The temperature ranges required by the different species are:
Ornate boxes: between 85°F to 88°F/day, 70°F to 75°F/night;
Other U.S. box turtles: 85°F to 88°F/day, 70° to 75°F/night.
Chinese boxes: 75°F to 85°F;
Malayans: water temperature 78°F-85°F and air temperature 85°F.
If you cannot get or keep the water consistently hot enough with the substrate and overhead heat sources, you need to invest in a submersible water heater. Buy a couple of aquarium or reptile thermometers; they are much cheaper than paying veterinarian expenses or replacing a dead turtle.
Full-spectrum lighting is required in addition to any light used to provide heat. Full-spectrum light mimics the beneficial effects of sunlight, enabling the reptile to metabolize vitamin D3. There are full-spectrum lights made for reptiles. Some are screw-in types that will fit into properly rated incandescent sockets; others are tubes, which slip into fluorescent fixtures. The full-spectrum is an essential part of the calcium metabolization process. With out the specific wavelengths and proper diet, calcium deficiencies will result which may ultimately prove fatal. Use a timer to turn the lights on and off; they need to be on 12 to 14 hours each day.
Note that the UV waves cannot pass through glass, and 40% of the available waves are lost when the light passes through an aluminum screen; try to have the light shining directly on them.
The best time to offer food is after the turtles have had several hours to warm up in the morning. Offer food daily to youngsters, every other day to adults. Since turtles are motivated by sight and smell, offer a varied, colorful diet. At each feeding, there must be both plant matter and animal products. Add vitamin supplement (such as Reptivite) twice a week.
A variety of vegetables, greens and fruits must be offered. A grated/shredded salad of carrots or orange squash, green beans, soaked, mashed high quality dog kibble, and fruit (such as strawberries, raspberries, cranberries, blackberries, cherries, and plums) should be all mixed together. Serve with some cantaloupe (with the rind), mustard, dandelion and collard greens. For treats, add flowers (hibiscus, rose petals, geraniums, and nasturtiums). Occasionally, offer chard, sweet peppers, leftover vegetables and fruits from your meals.
Many diets recommend high quality (low fat) canned dog food (especially chicken); finely chopped cooked chicken or raw beef heart. Most turtle people, however, prefer to supplement protein by feeding several freshly molted king meal worms Zoophoba king worms or Tenebrio meal worms (the tough brown exoskeletons are not digestible); earthworms and night crawlers (avoid bait shop worms - these are usually raised under rabbit hutches and are filthy with bacteria and protozoa); small pinky mice; slugs and snails (if caught in your garden, feed the snails and slugs for 4 days on dark leafy green vegetables - any that have been exposed to poisons will die in that time) and crickets (which have been fed on tropical fish flakes and fresh fruit for at least 24 hours). Remember that young turtles eat more animal matter than do adults, so the amount of protein offered should decrease over time until it is no more than 10% of total food volume.
Watch your turtle for any signs of illness: cloudy, closed or swollen eyes; swollen cheeks; open mouth breathing; bubbly mucous around the nose or mouth; runny stools; loss of appetite; listlessness; spots appearing on plastron (bottom shell), carapace or body; soft shell or excessive shedding or sloughing of skin or scales; buildup of food and dead skin around head and neck, and weight loss. Newly acquired turtles are under a lot of stress and may be riddled with bacterial or parasitical infections that may be passed along to you or your kids. Always take a sick turtle to a reptile veterinarian, and have your children checked out by their physician if they begin to exhibit any signs of illness (nausea, stomach aches, vomiting). Always wash your hands after handling the turtle and objects in the turtle tank. Make sure your kids wash carefully in hot soapy water - young children especially are susceptible to salmonella infections.
After bringing home and placing your turtle in its already-established tank, let it get used to its new surroundings for several days. It may spend the first couple of days closed tight in its shell, or may quickly withdraw when it sees you looming overhead or approaching the enclosure.
During this time, put fresh food out every day (on a large jar lid or in a shallow bowl), and make sure the water stays warm and clean. After a while, the healthier turtle will begin to explore its surroundings, and may begin to watch the goings-on around it.
When you pick up the turtle, support its body with both hands. Turtles feel more secure when they can feel something beneath their feet; "swimming" in air - "cute" though it may be - is stressful to them. Let them feel your hands or fingers beneath their feet. A two-handed carry will also help ensure that they will not suffer a potentially crippling--or fatal--fall.
When your children's hands are big and steady enough, teach them the proper way to hold and carry the turtle, and to wash their hands after handling the turtle. If they have been playing with any other animals before they go to handle the turtle, they should wash their hands before handling the turtle, too.
Scientists believe that many cold-blooded animals, especially turtles and tortoises, can live almost forever (well, one hundred years, at least) as they show no signs of aging as they get older. They die from being successfully attacked by one of their few natural predators, from the poisoning or destruction of their natural habitat and improper captive care.