At first Dumbork was housed in a 2.5 gallon used tank. After realizing that this is way too small, we upgraded to a brand new 15 gallon tank. I know that this is still very small for Dumbork (Male RES can get into 10-12 inches in length, fully grown). When he reaches 4 inches, we will try to upgrade to a 50 gallon tank. The dimensions of the tank are 24 x 12 x 12 (L x W x H). The ideal gallon size for a male RES is 90 gallons.