Sep 30, 2011

Posted by in Filters, Fish | 2 Comments

Aquarium Filtration


What is the right filter for my aquarium?

Choosing the right filter for your aquarium can be a daunting task. Here at Big Al’s, we have made it easier by providing you (the hobbyist) with the basic principals of aquarium filtration & the different functions each filter provides.

Before choosing the right filter for your aquarium, it is best to understand why a filter is needed in the first place.
A filter is used to combat and correct small changes in water chemistry, and clarity that occur in a closed system (Aquarium).

These changes include:

  • The accumulation of toxins in your water from the decomposition of organic matter such as fish excrement, plant wastes and excess food.
  • The accumulation of free floating particulates and debris that prevent crystal clear water.

These changes are corrected through three different stages of filtration:

  • Mechanical
  • Chemical
  • Biological

Mechanical filtration is generally the first stage that water must pass through to insure clean and clear water. It is responsible for the removal of particulate matter. This is achieved by passing water through a medium such as floss, foam, or diatomaceous earth which traps the debris. It also aids the biological stage by pre-filtering the water, removing gunk that could clog your biological media, and interfere with bacterial processes.

Chemical filtration is the removal of dissolved compounds from the aquarium water by a means of absorption, via various types of media. Many filters provide chemical filtration by including special media in the filter compartment such as carbon, which removes colours, odours, and other contaminants. Different varieties of chemical media can be used to remove other contaminants (i.e. algae causing nutrients such as phosphates and silicates).

 Biological filtration is the most important stage in filtration. This stage is responsible for converting toxic ammonia produced by living aquatic animals and the decay of proteins into less-harmful nitrates through the cultivation of nitrifying bacteria in the aquarium system. This process is known as the Nitrogen Cycle. Porous materials such as ceramic cylinders, bio balls, or substrates are optimal. The porous media allows for greater surface area for bacteria to colonize. Although not as common, there are types of biological filtration available (known as nitrate reactors) that complete the nitrogen cycle and allow the conversion of nitrates into harmless nitrogen gas that leaves the system naturally. These nitrate ‘reactors’ tend to be difficult to work with.

Now that we understand why filtration is important, and how it each stage works to benefit our aquarium, we can look into different ways to apply these stages to our aquariums through different types of modern filtration methods.

Internal Filters
Internal filters come in two primary forms: one form is essentially a powerhead with a media container attached to the intake to pre-filter the water before it goes into the pump. This is a true internal filter, able to be placed anywhere in the aquarium; even lying on its side. The other form uses a pump at the bottom of the filter body to push water up through the media and then back out into the aquarium. Not as versatile as the first form, but still inside the aquarium for operation; perfect for shallow water applications such as terrariums or paludariums. Internal filters provide mechanical and chemical filtration, but lack substantial  biological filtration. They are best suited for tanks with less than 55 gallons of water.

Power Filters
Power filters (also known as HOT “Hang-On-Tank” filters) are the most commonly used form of filtration. These filters hang off the back or side of the aquarium and draw water into the filter chamber, circulate it through the media, then push it back out into the aquarium. Most power filters incorporate all three forms of filtration (Mechanical, Chemical, and Biological) in the form of convenient pre-made filter cartridges that are easy to maintain. These cartridges are affordable, but tend to need replacement more frequently then some other types of filters. Power filters are best suited for aquariums under 100 gallons that will be lightly stocked.

Canister Filters
Canister filters are larger, more efficient filters that can be placed under the aquarium and out of sight. They are able to hold more, and a greater variety of media than either power or internal filters; this makes them much more versatile and better suited for larger, or heavily stocked aquariums. They require less frequent maintenance,  lasting for up to 4 times longer than other types of filters which can add up to big savings on replacement media. Canister filters can be used for aquariums as small as 20 gallons, up to aquariums as large as 400 gallons. They initial investment will be higher than other types of filters, but the difference in filtration power and savings in media replacements is worth its weight in gold!

Wet/Dry Filters
Wet/Dry filters come in the form of specialized canister filters and sump filtration systems. The canister variety uses a float switch mechanism to purge the canister allowing it to fill with air, giving the aerobic bacteria colonizing the biological media plenty of contact with oxygen before filling back up with water. This process happens continually while the canister is operating. Sump systems typically use a method where the media is held out of the water, and the water coming into the filter is poured or “trickled” overtop of the media allowing for constant exposure to oxygen. These systems are kept below the aquarium and out of sight, so as not to detract from the beauty of the aquarium. Although they are usually more complicated to set up, and are generally the largest overall investment, the benefits of Wet/Dry filters can be significant.

Protein Skimmers
Protein skimmers work through a process called foam fractionation, a process where hydrophobic molecules (protein wastes) are separated from the water before they begin to break down; this differs from most filters which facilitate the chemical break down of wastes. Protein skimmers are used almost exclusively in saltwater aquarium applications. This is because freshwater is not as dense as saltwater, and the tiny micro-bubbles required for foam fractionation can not be achieved. The skimmer’s purpose is to effectively increase the longevity of the aquarium water, as well as filter media in marine applications. They are essential for marine and reef applications where pristine water quality is needed for sensitive fish and invertebrates to survive.

With a thorough understanding of how filtration works, and the types of modern filtration that are readily available, making a decision on what type of filtration will work best for your personal aquarium becomes much easier. Do not forget, Big Al’s staff memebers are always happy to help you with any questions you may have, so do not hesitate to call or email us! 1-888-824-4257 or

  1. nancy block says:

    Everclear filter,10 gal? Or some modified gravel filtersand plate air pump a strong one , heater aqoion 150 watts tubing air difusers

  2. nancy block says:

    Everclean filterdo youvcarry thoes for a 10 gal glass aquirum;

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