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
75 450+ gal/hr
90 540+ gal/hr

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.

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comments (4)

  • I have a 29 gallon aquarium that holds 6 small to medium goldfish+koi, filter and medium gravel. Any suggestions on what kind and how many powerheads to put in it.

  • In a 29 gallon aquarium with goldfish and Koi, I would not recommend the use of a powerhead. The filter on your aquarium should provide enough water movement, and adding a power head may provide too much current which may disturb the fish.

  • I have a 120 gal freshwater Malawi/Tanganyika cichlid tank. Lots of caves, hiding places, etc. 2 Fluvals, large bio load clear water, do water changes, vacuum fine sand substrate once a month, rinse fluvals one every other week. My husband has kept lots of both reef and fresh tanks, but just hates the work involved so he swore off it. He told me that the tank was smelling like an old lake, like some of the ones in Texas. He suggested water circulation, so I got an ok one, and first put it slightly above the water to drive the o2 into the water. Awesomely good. Problem is, it seems to stress the fish in my 55 gal at work, where I have a better koralia evolution. I know to keep a tank healthy for the amount of cichlids I have, I have to make sure the filtration and circulation is good. Detritus still builds up in the other one though at the opposite end of the circulator. Is it ok to keep it above the water line slightly to cause max o2 diffusion into the water?

    Also, off the subject, I took in someone's small retail catfish as a rescue, but of course didn't do my homework about it, now it is 2.5 feet and BIG. Of course THIS has to be my husband favorite fish and the only one HE really likes now. Large bioload, ate a stunned dubosi once, but otherwise the other fish give him wide berth. How to keep him and keep him in a clear tank rather than a pond? I have read all about them NOW and it doesn't look good if they can grow to 7 feet. Monster fish keeping was never ever my desire, but it really seems to make large tank ownership doable. Any suggestions? Thank you, Stephanie

  • Hi Stephanie

    Sorry it took me the weekend to get back to you. I had to talk to some of our fish specialists. In cases like these, there are always more questions than answers, but I will try to answer as much as possible.

    If you are just rinsing the Fluvals, you should do one every other week. So, Week 1, you do Fluval A, and Week 2, you do Fluval B. Week 3 would be Fluval A again, etc. It also kind of sounds like you might not be replacing the carbon media? Carbon is usually what keeps the smell down in an aquarium. The heavier the bio-load you have, the more often you need to change the carbon. When you are rinsing, make sure you are using de-chlorinated water, as the chlorine can kill healthy bacteria that keeps the water in check. If you haven't done any water tests, you should test for Ammonia, pH, nitrates, and nitrites. You can find at-home testing kits at OR you can take a water sample to a local pet store that has aquariums. They *should* do a free water test for you.

    In terms of the catfish, is it in the 120 gallon? It would be better for it be in the 120 gallon than the 55 gallon. Get it used to eating pellet as much as possible so it doesn't get used to eating fish. Also, as long as it stays full, it is LESS likely to eat other fish – it may still eat some fish, but it is LESS likely to do so. In terms of size, Red Tail Catfish usually top out at about 3 feet in aquariums. So, it may not be the monster that you feared.

    I hope that helps! Feel free to call our Fish Tech at 1-800-737-3868 – just ask for Don.

    Thanks –

comments (4)

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