It is a 55 I believe. I have about 65 to 70 lbs. of live and base rock, some shooms, zoos, rics. I am setting up a 135 gal. right now as well. I am building it into the a wall under my stairwell, so all of the eqpt. wil be hidden yet easily accessable. What an addictive hobby!!!! My wife complains about the $$$$$ spent, but she is always wowwing over the tanks and showing them off. Thanks for all your thoughts and replies. Have a great day!!!!! Back to cleaning the tanks!