Many fish tanks, especially saltwater reef tanks, require extra water flow to oxygenate water and prevent waste from settling. A fish tank powerhead pump sits inside the aquarium and circulates water at a high rate. A nano powerhead is used for a small fish tank. The Hydor Koralia powerhead series is a best seller. A controllable powerhead is like a small aquarium wave maker. The random or pulsing flow creates waves or random currents in the water to simulate a natural reef environment
Want to know how much circulation for reef tank is needed? Most freshwater aquariums need 3–5x water turnover per hour. A fish only marine aquarium needs 10x turnover. Some reef tanks have more than 50x turnover/hour.