A return pump, feed pump or even a recirculation pump must be powerful and quiet. How strong the recirculation pump should be and what service it should yield depends on the personal taste and aquarium. Normally a value between three-fold and five-fold of the tank volume per hour is recommended. A 500l aquarium should support between 1.500l / h and 2.500 l/h. Since a recirculation pump runs for 24h and 365 days in a year, energy-saving recirculation pumps are especially preferred. Specially Tunze Silence, Royal Exclusiv and NYOS Viper pumps are recommended and also Aqua Medic and Aquabee pumps are very popular.