Properly Aerating Your Aquarium
Published March 27, 2008
Written by Katherine Barrington
Learn the basics of aeration and how to properly aerate your aquarium.
In nature, fish live in oceans, lakes, ponds, and rivers. These bodies of water all have large surface areas and sometimes large currents as well. This serves to oxygenate the water so that fish survival is possible. However, in an aquarium, the surface of the water is greatly reduced. Therefore, artificial ways of oxygenating he water must be accomplished through aeration. There are several ways to aerate your aquarium and these methods will be discussed in this article.
Before discussing specific methods, it is important to address the surface area of the water surface in your aquarium. The greater this surface area is, the more water that is in contact with the air at any given moment. This leads to greater oxygen absorption by the water. Therefore, you should try to maximize the surface area in your aquarium. People sometimes think, “If I can put x number of fish in a 20 gallon, then I should be able to put the same number of fish in a 20 gallon tall aquarium.” However, the 20 gallon actually has a larger surface area due to its length and width dimensions. You need to be careful with tall tanks or irregularly-shaped tanks (such as hexagons) as the water surface can be fairly small. This smaller surface limits the stocking capacity of the aquarium.
Oxygen/Carbon Dioxide Exchange Basics
At the water’s surface, oxygen and carbon dioxide are exchanged. Carbon dioxide goes from the water to the air. This is important because the carbon dioxide concentration in the water is raised as it is produced by fish. The fish would die if the CO2 was never allowed to escape into the atmosphere.
While CO2 is going from the water to the air, oxygen is going from the air to the water. This is important as it provides oxygen to the water that is needed by fish.
For this gas exchange to occur, the surface tension of the water must be broken. Agitating the surface breaks this surface tension and allows for a proper exchange of gases.
Temperature and Oxygen Concentration
As the temperature of your aquarium increases, the oxygen content in it decreases. Therefore, the higher you keep your tank’s temperature, the more aware you need to be of whether or not your fish are getting enough oxygen. Once you get above 800 F, you will probably have to provide some of the aeration devices listed below in addition to your filter.
For many aquariums, a simple HOB (hang on back) filter will adequately aerate your tank. Many filters have outputs that drop the water into the surface of the tank and, therefore, provide adequate surface agitation. This surface disturbance increases the surface area in contact with the atmosphere and, therefore, increases the oxygen absorption. The surface agitation also breaks the surface tension of the water as described above.
Additionally, the filter circulates the water in your tank. This is important because it moves the water at the bottom of your aquarium (water that is not gaining oxygen from the air) and moves it to the top surface so it can increase its oxygen concentration.
If your filter is not disturbing the surface enough or providing enough circulation, you can use a power head as well. A power head intakes water and mixes it with air as it is expelled. Many power heads also let you adjust how much air they intake which enables you to adjust how many bubbles are produced (see the paragraph on air stones below to see how bubbles help in aeration).
Power heads can also be useful in eliminating dead spots. Many times with a HOB filter, there will be areas in the tank that get little circulation. A carefully placed power head can serve to increase the circulation in these areas of your tank.
Filters, air stones, and decorations often do not adequately aerate large aquariums. Therefore, power heads are often the preferred method for larger tanks. However, you can easily provide too much current in small to medium sized aquarium with power heads so be sure to buy one rated for smaller tanks or buy one that has an adjustable flow rate.
Air stones are connected to pumps to produce bubbles in an aquarium. Many think these pumps are too noisy and, therefore, choose not to use air stones. However, placing the pump on a sponge will usually dampen the noise significantly.
Some hobbyist really like the look of a bubble wall in their aquarium and, therefore, use them even when further aeration is not needed. You can really add a nice look with these devices.
Air stones are placed in an aquarium to produce bubbles. It is not actually the bubbles that provide the oxygen to the water (a common misconception), but it is their disturbance of the surface and ability to provide more water circulation that helps to raise the concentration of oxygen in the tank.
Who doesn’t like a nice pirate ship that moves back and forth while simultaneously producing bubbles? How about a nice treasure chest? Or a fake shell? If you don’t like the natural look, but instead love putting these kinds of decorations in your aquarium, they can serve the same purpose as an air stone, with a little more flair.
How to Tell if Your Fish do not Have Enough Oxygen
It is sometimes difficult to tell whether you are giving your fish enough oxygen. The most telling sign that you are not is if you see them gasping at the surface. They will also tend to hang out back by the filter output. This area of your tank tends to possess the highest oxygen concentration as it is near the most disturbed surface. Another indicator is if you see bottom-dwelling fish constantly having to go to the upper part of the aquarium. If you see any of these indicators, use one of the methods described above to provide more oxygen to your fish.
How to Tell if You Have Too Much Circulation
You can also provide too much circulation in your aquarium. Obviously, if you see your fish being whisked around the aquarium or see them greatly struggling, you need to reduce the amount of circulation. Different species will be able to handle more water movement than others. Some fish (such as bettas, for example) prefer very still water so a small amount of current may be too much for them. Others actually prefer strong currents to play in. Research your specific fish and observe their behavior to see what they like.
Also, aquariums with live plants may not like a high oxygen concentration because it reduces the carbon dioxide concentration. If your plants are dying, one possible reason could be a lack of CO2.
Properly aerating your aquarium allows you to house healthy fish. The most commonly used devices are filters, power heads, air stones, and aerating decorations. Use whatever combination you like to provide your fish with the oxygen they require.
For additional information, refer to the following web pages:
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