Powerful powerheads are the basic pre-requisite for a marine aquarium. In case of tanks with high hard coral stock, it is the rule of thumb that about 20 times the aquarium volume should be circulated per hour. In case of high coral stock it is recommended to install several water flow pumps in the aquarium so that different water flow patterns can be simulated. For smaller aquarium, simple mechanically controlled water flow pumps are quite sufficient (e.g.Eheim StreamOn, Tunze Nanostream 6015, 6020, 6025, 6040, Hydor Koralia Nano). For a large marine aquarium wirth high hard coral stock, powerful, electronically controlled water flow pumps are recommended. On our marine online shop you will find the complete spectrum of water flow pumps from the cheap Aqua Medic Eco Drift 4.0 or 8.0 to Jebao / Jecod Stream Pump RW-4, 8, 15, 20 as well as the Tunze Stream 6055 and 6065 up to the high end pumps like the Ecotech Marine VorTech MP10 QD and MP40 QD Quiet Drive pumps.