Aquarium Filtration

Aquarium Filter Function

The function of an aquarium filter is to clean the fish's environment.

Chemical toxins and tiny particles are separated from the aquarium water.

The removal of such agents allows water quality to remain within an acceptable level for your fish.

Aquarium filtration is essential in most aquariums.

Larger aquariums with a range of healthy aquatic plants can function without a filter but the number of fish must be kept minimal.

Use of aquarium filtration will raise the maximum biological loading and allow the aquarium to house more fish.

Aquarium filters can work in a number of ways and often produce more than one form of filtration.

Mechanical Aquarium Filtration

Mechanical filtration is when solids such as fish food or excretions are separated from the aquarium water. These filters works like a sieve, catching the solid particles but letting the water flow through.

Sponges, polyester fibre or other similar media are housed inside the filter ready to trap the particles. Water is drawn through the filter media by a pump or flow of bubbles. The rate of water flow will be reduced as these particles are filtered from the aquarium water. As the sponges or fibre become clogged they should be cleaned or replaced to maintain maximum efficiency.

Chemical Aquarium Filtration

Chemical filtration harnesses reactions between compounds to capture aquarium toxins. These reactions occur as water is drawn through the filter chemical filter media.

Activated carbon or regular carbon is a common substance for this purpose. It can absorb chemicals found in fish waste and hold them until the carbon is removed. The carbon has a finite lifespan and should be replaced regularly.

Activated carbon can also absorb other chemicals in the aquarium such as chlorine and heavy metals. Aquarium medications will be absorbed also. For this reason carbon should be removed prior to treatment. Alternately the activated carbon can be used to absorb the medications once treatment is complete.

Biological Filtration

Biological filtration relies on micro-organisms to process toxic chemicals into less toxic compounds. This usually involves ammonia being broken down into nitrite then nitrate. If plants or algae are present in the aquarium they will take the filtration a further step by using the nitrate as a growth nutrient.

Biological filtration occurs in filters after bacteria have had time to colonise and multiply. The same filter media used in mechanical filtration is an excellent site for these bacteria. Water is again drawn or bubbled over the media allowing the bacteria to process the toxins.

When cleaning filter media it is important to allow as many of these bacteria to live. In doing so your filter will return to full efficiency more rapidly.

Rinse the media in water taken from the aquarium where the filter is kept. By doing this instead of using tap water the beneficial micro-organisms will not be harmed by chlorine or environmental fluctuations. Also see aquarium maturation for information about biological filtration.

Filter Capacity

The size of the filter system required will be determined by your individual situation. When choosing a filter consider:

- The size of the aquarium
- What turbulence level your fish prefer
- How often you want to clean the filter.
- The amount and type of fish food you put into the system

Aquarium Size and Filter Choice

Most filter manufacturers will describe a filter's size by the number of liters per hour (LPH) that it will process. Keep in mind that this LPH rating will reduce as the filter collects waste and becomes gummed up. As a general rule of thumb aim for your water to be processed twice every hour.

Where possible, avoid using only one filter in larger aquariums. Large tanks will be better equipped with two or more smaller capacity filters. The combined media volume will usually be greater than just one large filter. Splitting the filtration between two filter units also provide a back up if one filter fails.

Water Turbulence

Smaller fish and highly ornamental species will cower in corners if your filter is making a strong current. You can avoid a whirlpool effect by changing the direction of your filter's water outlet, using a spray bar return or choosing a lower capacity filter.

Filter Cleaning Frequency

Media volume may vary in different filters even when they have the same LPH rating. Choose a filter with the largest filter media volume possible for the LPH required. The smaller the filter media volume, the sooner it will be clogged and require cleaning.  Some filters have add on canisters allowing you to stack several sponges to increase the total volume.

When the water flow has diminished significantly filter cleaning is required. You will need to clean the sponge or other media and change any charcoal.

Food and Filters

Feeding only the required amount of fish food will require less filtration than abundant feedings. As a general rule feed only what they will eat in 5 minutes, but stop before 5 minutes if they stop eating. Do this once a day for coldwater and twice a day for topical fish.

The strain on your filter will be relative to the amount and type of food you put into your aquarium. High fibre pellet food pellets & vegetables will choke a filter faster than lower fibre granules.

Aquarium Filter Pages

Below are some of the filter varieties available for aquariums. You can read more about each type or go directly the our page containing all filters being sold. Specific filters have been created for a number of situations. Note that some types require an air pump to power the filter.

External Canister Filtration
Canister Filters

An external canister filter is the reliable choice for large size aquariums.

Internal Power Models

Internal power filters are versatile filtration units which often include a spray bar.

Sponge

A sponge filter is useful in aquariums housing fish fry or for use in hospital tanks.

Goldfish Bowl Filter

Small under gravel filters are useful for improving goldfish bowl water quality.

Undergravel

The undergravel style of filter lies beneath the aquarium substrate. They draw the water through the gravel.

Reverse Undergravel Filter

A twist on traditional undergravel filters.

Box Corner Filter

Box filters hold fibre media and activated. charcoal. Water is drawn inside and exits at the top.

Sump Filter

A sump or trickle filter sits outside the tank and provides layers of media for water to pass through.

Filter Media Pages

Fiber Wool Media

Filter fiber is a useful medium in box filters and other filtration devices designed for it's use

Activated & Regular Carbon

Filter carbon can adsorb some of the harmful fish waste and also acts as a biological filtration site.

Cartridge Refill

Some filters require filter media cartridges to replenish old inserts.

Bio Balls

This filter media consists of channelled plastic spheres that act as a biological filtration site.

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