In nature, water is constantly moving. This process must be reproduced in the aquarium if the aquarist wants to be successful. Water movement helps to keep plants and sessile animals from becoming covered in debris. It also insures that nutrients are dispersed evenly throughout the aquarium, helping to prevent algae blooms from starting in areas where detritus is allowed to build up.
A number of ways to create water movement are available to the hobby. The return from your filtration system makes a great start. As we start to deal with larger aquariums, however, supplemental water movement becomes increasingly necessary. Powerheads provide an economical solution for this need. The best rule of thumb to follow is that your aquarium water should be turned over 6 to 10 times per hour, as a minimum. In a mini-reef aquarium, you may want as much as 30-40 times turnover! With 55 gallon and larger aquariums, the use of multiple powerheads allows the greatest flexibility for the aquarist. If using multiple powerheads, add the flow rates of each to find the total water movement of the aquarium.
|Aquarium Size||Flow Rate||Power Head Manufacturers|
|20||120+ gal/hr||Marineland MaxiJet Powerheads|
|29||174+ gal/hr||Hagen AquaClear Powerheads|
|55||330+ gal/hr||Marineland Penguin Powerheads|
A common feature with powerheads is venturi controls. This allows air to be mixed with the water for aeration of the aquarium. This feature should NOT be used with planted aquariums, as it will deplete the amount of Carbon Dioxide (CO2) available for the plants to use in photosynthesis. It is also usually impractical for marine aquariums because it can cause excessive evaporation and salt creep to develop along the top of the aquarium.
Vertical water movement due to heating plays a subtle but important role in the planted aquarium. The use of a heater cable below the substrate will keep the substrate and adjacent water warm. It is the nature of warm water to rise, giving subtle vertical water current in the non-heated areas. Positioning any additional heaters low in the aquarium will also help with this.
Different plants and animals will prefer varying amounts of water movement around them. The output of the powerhead can be aimed to create the desired effect. The Koralia and SEIO pumps have large diameter water exhausts, not a small “jet” outlet. This allows them to push a much larger volume of water without creating a sand-blasting effect. The new Evolution pumps’ design can be used with wave makers for timed, on-off cycles. This is particular useful in the mini-reef aquarium.