Why do fish tanks need air pumps

Aquarium Air Pumps

Air Pumps for Aquarium Use - What Are They for and Why Are They Necessary?

(The First Tank Guide)

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What Is an Air Pump?

OK, this one's relatively simple. An air pump is a device used to move air, possibly under pressure. Typical aquarium air pumps move air by using an electromagnet to rapidly vibrate a rubber diaphragm. Unfortunately, this has the side effect of creating noise as well as moving air.

Do I Need an Air Pump for My Fish Tank?

Why would you want an air pump for your aquarium? Well, there are many uses of an air pump.

  • Some action ornaments are moved by air passing through them, turning valves, spinning wheels, lifting things, or whatever.
  • Some people like to have air stones in the tank which just bubble or give off a fine mist of air.
  • Some filters, such as corner filters and under gravel filters are (or can be) driven by air and would require an air pump. Some of these can also be driven by water pumps.
  • Some underwater habitats for semi-aquatic animals, such as Newts, Crabs, Mudskippers, and some Frogs or Shrimp, also require an air pump to keep fresh air circulating into the enclosure so that these animals do not crawl out into an unaerated environment.
  • Air pumps can also be used to create a current in the water, to prevent parts of the tank from becoming stagnant.
  • Air pumps are required for some types of protein skimmers to operate in marine tanks.

Are Air Pumps Necessary for an Aquarium?

That depends on what you mean. If you have a filter that is run by an air pump, then the air pump is necessary, as without it the filter will not operate and you are not going to be gaining benefit from having that filter on your fish tank.

If you have an action ornament that is run by an air pump, and you wish to have it operating as designed, then, again, the air pump is necessary.

If you wish to have an air stone giving off a cascade of bubbles as a decoration in your tank, than, again, the air pump to run this air stone is arguably necessary.

One of the most common misconceptions in the aquarium hobby, possibly second only to "fish will not outgrow their aquarium", is that you need an air pump and air stones to provide sufficient oxygenation to that tank to keep the fish healthy, and that the air pump provides oxygen to the water. In fact, the air pump is not necessary to keeping fish, except as noted above. An air pump will not directly put oxygen into the water, what it will do is two things:

  1. Increase surface area
  2. Improve circulation

Gas exchange - where the water dissolves oxygen and other gases from the air and releases excess carbon dioxide and other gases to the air - occurs over any and all surface area where the water has contact with air. By increasing the surface area of the water, each bubble gives the water further opportunity to release carbon dioxide and take up oxygen. However, this improvement from an air pump is shadowed by the improvement in circulation that the air pump can effect. The improved circulation will move highly oxygenated water from the surface lower in the tank allowing water with more carbon dioxide and less oxygen to the surface of the tank where id can release its carbon dioxide and take up oxygen. Of course, if you already have a good filter that is providing sufficient water circulation, then the benefit you will receive from an air pump is minimal.

Choosing the Right Air Pump

There is no hard and fast rule for choosing an air pump. Some air pumps are rated for different sizes of tanks, but these ratings are, actually, nearly irrelevant to choosing the correct air pump.

If you are using the air pump only to operate an under gravel filter, and your tank is a standard size, then the tank size ratings on an air pump are probably relevant. However, if you are doing anything else with the air pump, or if your tank is not a standard size, then the tank size ratings for an air pump are highly irrelevant.

Here are some guidelines to have in mind when you are choosing an air pump for your aquarium:

  • The more things you are running from your air pump, the larger air pump you will need, and conversely, the fewer things you are running from your air pump, the smaller air pump you will need.
  • If you tank is more than 18-20" (46-51cm) tall, you will need to get a special deep water air pump designed to push air that far below the water surface.
  • The more resistance the things you are pushing air through have to the air, the larger an air pump you will need. (Larger air stones will provide more resistance than smaller air stones, and any air stone will provide more resistance than no air stone. Also, some kinds of air stones will provide even more resistance than others of the same size.)

When choosing an air pump, pick one a little larger than you initially think you will need. This larger air pump will help you by compensating for underestimating when choosing the air pump or by providing a little room for expansion if you decide you want that later.

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April 7, 2003

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June 15, 2003

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