Located 6 meters directly under the tank, behind thick metal double-doors, it features four 25,000-liter/hour pumps to return the water from the sump back into the aquarium, after it’s been filtered. For cleaning he relies on gravity, with the water flowing down from the tank to create a foam from the impurities, which is then removed by a revolving paddle. A self-built frequency-controlled system connected to the pumps, controls the speed of the two return pumps to create waves in the tank. And that’s just the tip of the iceberg.