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Filtration: The basics

© Winston Vaughan Schoenfeld

One of the most common questions which I come across from new aquarists is "what filtration will work best for my aquarium?" Whether it be fresh, salt, or a reef aquarium which you are starting, it is very important to understand the different types of filtration which there are. There are three major types of filtration: biological, mechanical, and chemical. Most filtering systems either use one of these or a combination of the three. Biological filtration is the most complicated of the three. In order to understand biological filtration, it is helpful to first review the biological cycle of aquariums. Take a look at my previous editorials on the biological cycle of aquariums if you are not familiar with the biological cycle of aquariums. Biological filtration basically utilizes a process known as nitrification. This process is simply the natural biological process that occurs in saltwater aquariums, where ammonia is transformed to nitrite, and nitrite to nitrate. For biological filtration, a filtering system will simply supply a substrate for the nitrifying bacteria to colonize on. Mechanical filtration is the simplest of the three types of filtration. Mechanical filtration relies on a matrix material, such as fiber floss, to capture particles in the water which is passed through it. As a result, tiny particles are removed from the water, and gradually begin to accumulate in the matrix material. When a large number of particles have accumulated, the matrix material must be cleaned or replaced. Chemical filtration is the last of the three types of filtration. Chemical filtration relies on adsorption and adsorption of molecular compound in the water by a filter media. There are a vast number of filter medias, the most common of them being the tiny bubbles used by a protein skimmer, which attract molecular particles in the water, and cause them to collect in a container. Now that the three main types of filtration have been introduced, you can now understand the methods used by filtration systems for freshwater, saltwater, and reef aquariums. An understanding of the basic types of filtration is the first step in understanding what filtration devices work well for each different aquarium setup. In the next few editorials, I will take a look at some of the major (or more popular) filtration systems which aquarists have to choose from, and which systems work well together to provide good filtration for different types of aquariums.

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