The Salty Side: Saltwater Aquariums for Beginners

Powerheads & Gyres

It is essential to ensure that the water’s surface is constantly disturbed and that there is a constant movement of water within the water column of a saltwater aquarium.  In order to achieve this circulation of water within your saltwater aquarium, in addition to a return pump, you will need powerheads and/or gyres.  

What is the difference between a Powerhead and a Gyre?

A powerhead provides a constant line of direct flow.  Some powerheads have ball joints which mean that they can be swivelled into whatever direction you need.  Not all powerheads swivel, such as Ecotech Vortech, so you may have to play around with it’s placement. 

gyre, also known as a wavemaker, provides a broad, linear stream of flow in one direction.  This then bounces off the other side of the tank, creating a flow in the opposite direction.  The entire column of water can be displaced in this way which, depending on your rockwork, may eliminate the need of a powerhead.

FYI:  The term ‘gyre’ means large rotating current, as found in the ocean.

Powerhead and Gyre Placement

First off, I think it’s important to say that it may take some time in getting the water circulation right in your reef tank.  Every reefer’s tank is different, not only in size but general flow rates and rock placement.  There is no one-size-fits-all and the choice between using gyres and/or powerheads is a personal one, mostly owing to budget.

Gyres are generally placed near the top of the tank.  Depending on the size of your tank you may want to have two for larger tanks and one for a smaller tank.  

If using two, some reefers prefer the gyres to be placed horizontally opposite each other on the sides of the tank while others prefer them on the back walls of the tank, placed vertically.

Powerheads are usually placed between the middle and top, but may need to be moved around to determine best placement due to rock structure.  If you are using an an adjustable powerhead, you can just aim in whichever direction needed.


The best method of testing the effectiveness of your powerhead/gyre placement is by feeding your fish and watching what happens to the food itself.  Realistically speaking, all food should be eaten within 20 seconds, but have you noticed any of it ending up in a corner and settling on the sand?  No food should have the chance to settle at all.  This is an indication of inadequate flow or improper placement.   

Do I need a gyre AND a powerhead?

You can use either or both in your saltwater aquarium.  The aim of a gyre is to eliminate dead spots however, how you place your rockwork greatly impacts whether or not you will have dead spots in the first place.  If you do, this means that you may need to add a powerhead.

Gyres are certainly the way forward but do come with hefty price tags in comparison to powerheads.  I personally, for the size of my tank, 148 gallon (550 litre), use 2 gyres.  This gives detritus no opportunity to settle anywhere in the reef tank.  Allowing detritus to settle in your tank will result in algae and cyanobacteria. Gyres are also available for smaller tanks between 25 and 100 gallons. 

You can of course only use powerheads in your tank.  If using powerheads, you will need more than one in most aquariums.  I used three small powerheads in my first 25 gallon (97 litre) saltwater aquarium.  (These are best set to pulse mode, if available, and placed opposite each other but slightly offset.)  Powerheads are easy to move around and aim in the direction you want and they’re cheaper than gyres.

Hydor Koralia Nano Aquarium Circulation Pump, Includes Built-In Cable Protector, 565 GPH, Measures 2.4-Inches & is Ideal for Fresh or Salt Water Use
  • New and improved patented vibration absorbing magnet and suction cup support; Can safely hold the Koralia Nano 565 positioned in tanks with glass (or acrylic) up to 1/2" thick.
  • Flow rate of 565 gph; Ideal for fresh water aquariums from 40 to 65 gallons; Salt water acquariums 20-40 gallons
  • Power absorbed: 3.5 Watts. 50% less power consumption and up to 20% more water flow when compared to previous Koralia models

Why is water movement so important?

1. Gaseous Exchange

The primary purpose of water movement, ie. wavemakers, is to continually introduce fresh oxygen into your system while aiding in the disbursement of nitrogen gas created by the nitrogen cycle.

This process is known as gaseous exchange.  In the most simple terms, it is the exchange of one gas for another.  Without the constant supply of oxygen your fish would quickly utilize all available oxygen in the water and die.

2. Waste Management

Powerheads and gyres aid in keeping waste in your display suspended in the water column, effectively ensuring it does not settle anywhere on the live rock or sand.  Creating an environment conducive to effective waste management hinges not only on your powerhead placement, but also on your rock display.

In order for your choice of wavemakers and/or powerheads to work as efficiently as possible, there should be no structure inhibiting the flow it creates.  By planning your rock placement in conjunction with powerhead and/or gyre placement you will be eliminating any potential ‘dead spots’ in your tank.

Dead spots are areas where flow within these areas is not strong enough to lift waste and detritus from the floor and keep it suspended in the water.  Over time these dead spots accumulate detritus which cause algae and increased nitrates in the reef tank.

3. Coral

Powerheads and gyres help to mimic the natural flow that corals in particular come to rely on for continued health.  Coral, be they soft, LPS or SPS are immobile creatures. Without the aid of water flowing past them they would be unable to feed themselves and would not be able to shift unwanted foreign objects from themselves.

The flow of water helps them to take nourishment as and when required, and keep themselves clean in the process. In the case of SPS, strong flow is required at all times as a necessity.


Water movement is important when keeping a reef aquarium.  Return pumps will keep the water turning over but powerheads and gyres create powerful water circulation which prevents the build of detritus, promotes gaseous exchange and is extremely beneficial to coral.    

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