Very carefully! To open the feeder door, I cut 1 prong off the hinge so I can remove it easily. I also took the hinges off the rear of the lid so it will slide off to the side. The cabinet has an over hang in front so it looks like there is less room than there actually is. With the lid off there is room to put my arm into the tank well enough for glass cleaning. For the really big access I can slide the tank out the back, after draining of course. I wouldnt want to have to chase a fish around in there with a net though.