Water should be provided with a "drip-feed system" to prevent an accidental build-up of harmful molds in the tank environment. Although gerbils are adapted to the desert, they require water to be supplied at all times to be safe and healthy. Care should be taken not to introduce new smells suddenly into the tank, because the tank is considered by the gerbils to be their territory. Gerbils are active and appreciate a running or exercise wheel. Repetitive corner digging can be minimized by providing tunnels while gerbils are in their young, formative months. As with most animals, they appreciate a secure, private area that is dark for sleeping.