Box turtles need a good size enclosure in order to provide for the proper range of heating and humidity. The smallest size indoor enclosure one box turtle should be kept in is a standard 30 gallon breeder aquarium. For two box turtles, the minimum enclosure should be a 40 gallon breeder tank. Bigger is always better. A ten gallon aquarium is not appropriate for an adult box turtle and is analogous to forcing you to live in your closet.