here is a part of a good care sheet i found for you:
"HOUSING MUD TURTLES INDOORS - The most useful form of indoor accommodation for Kinosternon consists of an aquarium. Mud turtles do a great deal of “bottom walking”, because of this I suggest using shallow water to allow them to easily reach the surface to breathe. For hatchlings I would suggest a water depth of 2 to 4 inches (5 to 10 cm) with one end built up with rocks to provide a dry basking spot. It is possible that they will seldom use this. Mud turtles do very little basking but the addition of a shelf just below the surface of the water gives them another option to bask – in this case without leaving the water. A reasonable size aquarium for a hatchling is a 20 gallon: 30 inches by 12 inches, (75 cm by 30 cm). As the animal grows the size of this habitat should be increased. Water depth is not as critical as they get older but again, it should be remembered that they spend most of their time on the bottom so exceptional depth may stress them. A depth between 8 inches and 12 inches (20 cm to 30 cm) would be fine for adult turtles, which are between 4 inches (10 cm) and 9 inches (22 cm) , depending on the species. In addition a hiding place or cave under the surface of the water is something that will be readily used and lower stress. Make certain if this is made out of rockwork that it cannot collapse on the turtle. I find that half of a flowerpot works well for this purpose. "
that was taken from this site:
http://www.chelonia.org/Articles/kinosternidaecare.htm
