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MECHANICAL FILTRATION

Mechanical filtration is nothing more than removing many types of unwanted particulate matter from the system, by first trapping it in a dedicated location (or several such locations), and then cleaning those locations to remove the matter entirely from the tank and filters.

Merely moving it from inside the tank, where you can see it floating around in the water, to the filters, does not improve the water quality at all. The only thing such achieves, is removing it from your sight, but not from the water. Leaving particulate matter trapped in the mechanical filters for too long does, in fact, more damage than good, as once the trapped matter is concentrated in a small area, it can quickly deplete large amounts of oxygen from the water. This material may then start decaying in an anaerobic (anoxic - oxygen poor or oxygen depleted) manner. This can quickly add many compounds that are totally undesirable, and dangerous, to the water . These compounds result from break-down by-products. The better known one that you are probably familiar with is hydrogen sulfide, but there are many other such breakdown products that you do not want in the tank's water. Even small amounts of hydrogen sulfide lower the water quality enough, for your lifeforms not to look at their best.

Even if the decay that takes place does not remove all the oxygen (which it will in the extreme case), it can still remove considerable amounts, and lower dissolved oxygen to dangerous levels for all animal life you keep in the tank. They may not die, they will more than likely not, but they will just not look as good as they would, if the water quality were better.

It is all a matter of degree; the difference between a vibrant looking aquarium, and one that looks all right to you, but does not draw any oh's and ah's from your friends or visitors.

Mechanical filtration is, therefore, a two-step process : first you trap the dirt, detritus, floculate, particulate, (all names for what we are trying to remove) in a specially designed area by means of a screen, mesh, cartridge, floss, or other form of filter, and secondly you clean those filters regularly to remove that matter entirely from the system (the mass of water in your tank and filters). Doing so prevents whatever you trapped in the filters from breaking down, causing problems for you by lowering the water quality (usually evidenced by lower dissolved oxygen levels in the water). At the same time, because you prevented the decay, you also prevented the addition of other compounds that result from such decay, to the tank's water.

Some of these breakdown compounds may even be more toxic than the particulate matter that you trapped to begin with, obviating the need to clean your mechanical filters on a very regular basis. Once a week, or even more frequently, is strongly recommended.

Anything that can trap dirt acts as a mechanical filter, even materials in the tank and filters that you may not think about, e.g. the material used inside the trickle filter's biological filtration area (I am referring to material that is dense, close-meshed, or that packs and restricts the flow of the water, e.g. gravel).

Keep this in mind because, often, areas such as those never get cleaned, or they are cleaned much too infrequently. Examples are calcite layers in the bottom of filters, undergravel filters that are in dis-use or are used on a reduced flow rate, etc...

Mechanical filters come in many forms. They could be canisters filled with material such as EfiMech from Eheim, or Biomech from Kordon, filter floss, pads, blue-white bonded pads, bags; or they can be specially designed containers with pleated cartridges or bags, and many others still.

All work efficiently and will trap lots of detritus. The finer the material, the more it will remove, especially after it has accumulated some dirt already. As the spaces where the water can flow through get smaller, get restricted, finer and finer particles will be trapped. This will slow the flow of water through the material down as well, which is yet another reason why you should clean all such filters regularly.

Here is a short overview of the most common types of mechanical filtration methods used, and available to the Hobbyist. You should use at least one of them, but you may want to combine several in your system, for optimum efficiency.

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