The concept behind the performance of this reservoir: The Alphacool Geysir Double Power pump station is designed for installation of up to 2 Eheim submerged pumps. Either 2 Eheim 1000 or 600 pumps can be installed, depending on the reservoir.
How does this reservoir work? To use the reservoir, only one pump needs to be installed. For pump installation the top is removed, the pumps can be pushed in from below, and everything can be installed again.