Aquarium Filters-Choosing the Right Filter
Aquarium External Power Filters
External power filters have become the most commonly used filtration system in tanks up to 55 gallons. Most power filters provide all three types of needed filtration - mechanical, biological and chemical, and can provide all the filtration you will need. Many hobbyists use a power filter along with an undergravel filter to increase the biological filtration (and thus the number of fish they can keep) in smaller tanks. And many use power filters on even larger tanks in conjunction with canister and other filters.
An external power filter hangs on the back of your aquarium and is basically an electric pump that draws water from your aquarium and pumps it through a replaceable filter cartridge that is typically filled with activated carbon. The "carbon cartridge" traps any floating debris such as excess food, and provides the chemical and mechanical filtration. Biological filtration is accomplished by passing the water over a wheel, sponge, or porous plastic plate that houses the beneficial bacteria.
In some cases the beneficial bacteria live on the replaceable cartridge. You should only use a filter designed in this way with an undergravel filter as other biological filters since replacement of these cartridges removes the beneficial bacteria from your system.
Power filters come in different sizes and are rated by the number of gallons per hour that they can pump. This means the water should be circulated through the power filter a certain number of times per hour. It is recommended that the aquarium water be circulated through the power filter three to five times per hour.
For example, if you have a 20-gallon aquarium, you'll need a power filter that circulates up to 100 gallons per hour. For a 55-gallon aquarium, a power filter that circulates up to 300 gallons per hour would work best.
Most power filters are sold with at least one filter cartridge included. Some cartridges are reusable. They can be rinsed clean and the inside of the cartridge refilled with fresh carbon and/or filtering media, but most cartridges need to have the filter cartridge replaced on a regular basis. If you buy a filter that has reusable cartridges, be sure to rinse the cartridge in some of your aquarium water or in dechlorinated water. Chlorine will kill the beneficial bacteria that have developed on the filter cartridge. We suggest that the filter cartridge or media be changed at least every three to five weeks depending on the fish load and type of fish you are keeping.
Whenever you replace a filter cartridge, always rinse the filter cartridge before you put it in the power filter. If you don't do this, you'll have a black cloud of residue from the charcoal powder in the filter cartridge. This will likely blacken your clean aquarium water.
Canister filters are a very effective means of providing a total filtration system. Canister filtration is most typically used on 55-gallon aquariums and larger. While some canister filters are designed to hang on the back of your aquarium, most are designed to be put under the tank and hidden in the aquarium stand.
Many believe that an advantage of the canister filter is that it is hidden from sight and thus is more aesthetically pleasing. A major advantage of using a canister filter is the flexibility it gives you in adapting the filter to your other mechanical, biological and chemical filtration needs. These filters are designed to let you determine how much (and what type) of filtration media you want to use.
The only disadvantages are that it requires more hoses and connections than an external power filter and thus is more complicated to set up. Also, this type of filter must be disassembled to change fiiltration media and thus is somewhat more difficult to maintain. Recent designs from the major manufacturers have significantly improved the ease of set up and maintenance of these types of filters.
Power heads are typically used to improve the water flow through an undergravel filter. Using a power head with an undergravel filter can allow you to keep more fish without getting a bigger tank. A power head is used to circulate the water in your aquarium. Its main purpose is to help the undergravel filter do its job.
When used with an undergravel filter, a power head is placed on the top of an undergravel lift tube. It "powers" the undergravel filter by pulling the water down through the undergravel filter and up the lift tube where it is expelled out onto the surface of the water. Most power heads include an adjustable air vent to improve aeration of the water. If you use a power head, you don't need to use an air pump to power the undergravel filter. However, you'll still need an air pump if you want to power action ornaments or decorative air stones.
A power head can also be used as a stand-alone unit in the aquarium. It does not need to be placed on top of a lift tube and can be put in an aquarium for the sole purpose of circulating and aerating the water. Some power heads come with an attachment that turns a power head into a biological and mechanical filter
An undergravel filter is simply a slotted piece of plastic (undergravel plate) that sits on the bottom of the aquarium and lets water flow between the plate and the bottom of the tank. There is a tube that is attached to this bottom piece, known as the lift tube. Gravel is placed on top of the filter, and the filter, lift tube and gravel work together to provide filtration.
Water is pulled down to the bottom of the tank, through the gravel. And then the undergravel plate, then flows back up to the top through the lift tube. The water is again pulled down through the gravel. This allows beneficial bacteria to thrive on the oxygen laden water flowing through the gravel.