Hydor koralia nano evolution air pumps are circulation pumps that use modern technology to create natural water circulation and movement many of the creatures and plants in fresh or salt water aquariums prefer a continuous gentle flow of water the pump is fixed with patented special magnetic suction cups in the aquarium and can be freely directed the hydor koralia nano pump simulates the natural currents found in coral reefs the corals in salt water aquariums will benefit from these currents