Which airpump do I need for my tank?

Airpumps provide vital oxygen to coldwater, tropical and marine tanks. Here’s what you need to know:

Airpumps are really important pieces of kit for any aquarium. They help to oxygenate the water, drive off noxious gases and are just as important to filter bacteria as they are to fish. As well an airpump you’ll need airline (tubing) and an airstone, unless you’re connecting the airline to an air- operated sponge filter or air operated ornament.

Airstones 

Airstones have dual features as they create soothing streams of bubbles that rise up through the water, while also oxygenating at the same time. Contrary to popular belief, its not so much the bubbles themselves that oxygenate the water, as it is the act of the bubble breaking and agitating the surface of the water. All airpumps will run airstones but the size of the airpump is key to running the right size of airstone. Airstones can be up to 12”/30cm long, and air curtains much longer still, but they need a sufficiently powerful airpump to run them. Too small, and bubbles will not be emitted from the full length of the airstone.

Small airstones may float so need airline clips and suckers to keep them pinned to the glass. Airstones also degrade over time and disintegrate, so need replacement to keep the fine bubble production going. 

Accessories

Every airpump should be used in conjunction with an inline check valve, also known as a non-return valve. Airpumps are aften placed in the cabinet underneath the aquarium and are designed to pump one way. But when the power goes off a syphon starts and water flows backwards down the airline and into the airpump body. When this happens it will irreparably damage the pump, or worse. Check valves are inexpensive and essential, although they reduce the pumping power of the airpump, so it would pump less than it would do if not connected to the valve. One way to run an airpump without restriction from a valve is to mount the airpump above the aquarium. Do this and when the power goes off it won’t back syphon.

Airlines can also be split with T or Y connectors to form two airlines, although the air will take the easiest route. Control the amount of air going to each airline with an airline clamp or tap, or route a single airline to a manifold which will allow unlimited spitting and control of each individual line. Use 90-degree elbows on airline for a neat job.

Airpump selection

So an airpump has to be powerful enough to power the airstone you intend it to run, but you must also account for aquarium water depth, as the deeper the water, the more pressure the air has to pump at. And if you split airlines the water depth issue becomes twofold. 

Airpumps range in size but they all work basically the same way, by vibrating a rubber diaphragm inside. This diaphragm creates noise and vibration, so a good airpump manufacturer will do all they can to suppress the noise and vibration inside the design of the pump, including rubber feet and thick casing. If you want to run two airlines then a twin outlet pump is what you need. That would also enable running an airstone in two different tanks without having to split it yourself and losing pressure to both. And some pumps come with controllers built in, so you won’t need a clamp or inline tap to turn air flow up or down.

If you have very large aquaria that require lots of bubbles at depth, a pond airpump is probably for you.  

Noise

In general, the larger airpumps are, the noisier they are regardless of design, although this can be minimised to an extent by hanging the airpump off the ground if possible or by placing it on a firm, smooth surface, away from other objects that it could vibrate up against. Airpumps that vibrate so much they “walk” across a surface aren’t as good as those that don’t, and even an airline itself vibrating against something can cause noise. Silicone airline is softer than pvc airline so may alleviate this to an extent.    

Which one to buy

Investing in a decent airpump is not a false economy. It will run the airstone(s) that you need it to and premium-priced models tend to be quieter than cheaper ones. All airpumps can also be serviced by changing the small, felt air filter and rubber diaphragm if necessary. Check the performance of non-return valves too by blowing down them.

Tip

Run an airstone separate to your main filter and if the filter blocks and stops, your fish will still have a source of vital oxygen. 

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Jeremy Gay is an author, lifelong fishkeeper, and aquatic specialist. He's a former editor of Practical Fishkeeping Magazine, UK editor at Reefbuilders, a former aquatic store manager, and has collected fish in Sri Lanka and the Amazon. He's been on tv and radio, contributed to Koi Carp and Gardeners World magazines, been a product tester, a judge, and a product developer. Jeremy is here to guide and advise you on all things tropical, pond and marine, from set-up to stocking, health, feeding to breeding, as well as solving many common fishkeeping problems along the way.


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