William...just go into the tank and pop him into his water dish once a day. Or maybe even take him out and put him into a bigger bowl of water for a little swim time. Just make sure he can't get away...some garters like to swim and others jump right out of the bowl. Make sure you supervise carefully if he is going to swim. Also, misting plants several times a day can help...some garters will lick the water off of the plants.