What is Mechanical Filtration?

In the world of saltwater aquarium filtration, mechanical filters play a very important role in removing particulate matter from the aquarium water.  Physical debris such as fish poop, leftover food, free-floating algae, and pretty much anything else that might be floating around in the water.  Sponges, filter pads/socks, and protein skimmers are all examples of mechanical filtration in your aquarium. Anything that is physically removing undissolved particles. 

Why Is Mechanical Filtration Important?

When maintained properly, mechanical filtration is one of the most effective ways to remove organic waste (nitrate/phosphate) from the aquarium. By removing fish poo and any leftover food via a sponge or filter pad, you can effectively remove the waste before it is broken down into nitrate and phosphate. Through this process, mechanical filters will also polish the water making it clearer and more pleasant to look at! 

Most all successful saltwater aquarium filtration systems have some kind of mechanical filtration.

While it is possible to run a saltwater aquarium with minimal or no mechanical filtration,  it is typically only the case for very mature aquariums where other more advanced nitrate and phosphate removal techniques are employed; a large refugium, biodenitrator, or media reactor for example. 

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Types Of Mechanical Filtration


Cleaning and swapping out your mechanical filter materials is absolutely critical to its effectiveness. Since mechanical filters are catching debris, if that debris is left to sit in the aquarium water it will eventually be broken down into nitrate and phosphate, defeating the entire purpose.

A dirty filter sock is worse than no filter sock at all!

Therefore, you must clean out or replace your mechanical filters on a very regular basis. In most cases, filter pads, socks, and floss will need to be changed every 3-5 days or weekly at a very minimum. Filter sponges should be rinsed clean on a similar routine. If you wait until the filter material is completely clogged, you have waited too long. This is exactly why automatic filter rollers have become so popular, they eliminate the need for manual maintenance and only require that you remove and replace the filter roll on a +/-monthly basis. 

Can You Over-Filter Your Aquarium Water?

Yes! Although somewhat rare, it is indeed very possible to over-filter your water. Some levels of organics are required by the bacteria (biofiltration) and other organisms in your aquarium to function, especially in a reef tank with corals. As aquarium filtration technology has progressed over the years, the reality of over-filtration becomes more and more common. Running an aquarium with zero or undetectable levels of nitrate and phosphate leads to biological imbalance leaving room for algae and other pests like Cyanobacteria and dinoflagellates to takeover.

The key to success is balance and stability. The most ideal ratio of nitrate the phosphate is often debated, however, we do have some widely agreed upon ranges you should shoot for in your tank. Check out our Reef Tank Parameters chart for a complete list of acceptable water parameters.