Freshwater Aquarium Filters

Freshwater aquarium filters provide the best type of filtration for stability and reduction of toxic wastes. In nature, regular flowing freshwater makes it clean for fish to live in, but in an aquarium this does not happen and water will become foul. This is where Filter comes in. Although we cannot mimic everything as in nature, we can make water clean for fish to live in our aquarium. There are several different types of filtration that a filter can perform: mechanical, biological, chemical filtration. For details about types of filtration, checkout this article. Below are different types of filters that can be used in our aquarium.

Sponge Filters

Multiple sizes sponge filters

Multiple sizes sponge filters

Corner Filter

Corner Filter

Sponge filters work by passing water over a highly porous sponge where bacteria are allowed to grow. They are almost purely biological with some mechanical filtration provided by the sponge itself. The sponge should not be cleaned or allowed to dry out because this will kill the nitrifying bacteria. Sponge filters are good for breeding situations where very small fish are at risk of being sucked up by the strong intake currents of canister filters or overflows. They are also good for fish like bubble-eyed goldfish that may be injured by strong intake currents of power or canister filters. Sponge filters can be powered by air pumps or small water pumps.

Sponge filters have several variations including Corner Filters. Corner Filter sits in one corner of the aquarium. They can be used in small aquariums and breeding tanks effectively. It can be used for all three types of filtration mechanical, biological and chemical filtration.

Undergravel filters

Under Gravel Filter Basics

Under Gravel Filter Basics

One of the oldest types of filters, the undergravel filters consist of a porous plate which is placed beneath the gravel on the base of the aquarium and one, or more, uplift tubes. Historically, undergravel filters have been driven via air displacement. Air stones are placed at the base of uplift tubes which force water out of the uplift tube creating negative pressure beneath the undergravel filter plate (also called the plenum). Water then percolates down through the gravel which itself is the filtration material. Greater flow rate of water through the gravel can be achieved via the use of water pump rather than air displacement.

Beneficial bacteria colonize the gravel bed and provide biological filtration, using the substrate of the aquarium itself as a biological filter.

Undergravel filters can be detrimental to the health of aquatic plants. Fine substrates such as sand or peat may clog undergravel filters. Undergravel filters are not effective if the substrate bed is uneven. In an uneven gravel bed, water will flow only through the thin portions of the bed, leaving the more heavily covered areas to become anoxic.

Canister Filters

A commercially available canister filter

A commercially available canister filter

Canister-style external filters offer a greater quantity of filter materials to be used along with a greater degree of flexibility with respect to filter material choice. Water enters the canister filled with the chosen filter material through an intake pipe at the bottom of the canister, passes through the material, and is fed back to the aquarium through the return pipe. Water is forced to circulate through the filter by a pump typically installed at the top of the canister. It is important to note that canister filters are sealed, fully flooded systems, meaning that the aquarium, intake pipe, filter interior and the return pipe form a continuous body of water. In this configuration both the intake and return path form two siphons, which precisely counterbalance each other. Under these circumstances, the filter pump does not have to spend any effort to lift the water back to the aquarium, regardless of how high the latter is installed above the canister. The pump should only be powerful enough to push the water through the filtering material as well as overcome the drag in the intake and return pipes. This makes canister filter pumps virtually insensitive to the height difference between the aquarium and the filter (although exceeding the manufacturer-specified height limit can lead to leaks).

Benefits of this type of filter are that they can provide a high volume of filter material without reducing the internal space in the aquarium, and that they can be disconnected from the tank for cleaning/maintenance and replaced without disturbing the aquarium interior or occupants. Also, as a filter with external plumbing, it supports in-line installation of other aquarium equipment, such as water heaters and carbon dioxide diffusers. Such equipment can be removed from the tank and installed in-line into the return pipe of the filter. Disadvantages of canister filters include the increased cost and complexity relative to internal filters and difficulties in cleaning the tubes which transfer water to and from the aquarium.There is also the risk of a leak, which naturally is an issue for any filter placed outside of the aquarium.

Canister filters were initially designed to filter drinking water, under low pressure. Canister filters for aquariums use high water pressure, from a properly powered pump, to force water through the dense filter media. A pump can draw water from an under-poergravel filter, and run it into a canister for double filtration.

Powerheads

Powerhead

Powerhead

An aquarium powerhead is a water pump completely submerged into an aquarium to circulate water; usually this is used to create flow throughout the tank. For example a single powerhead could be used at one end of a freshwater aquarium to simulate a laminar river current, or multiple powerheads can be positioned throughout the aquarium to create more turbulent flow. A switching or variable-voltage system (also known as a “wavemaker”) is commonly used in reef aquariam to more closely simulate the movement of ocean water. Water circulation is vital to proper biological filtration of most saltwater aquariam, and is useful in freshwater aquarium for allowing free-swimming fish adequate exercise.

Power Filters

Standard Power filters use disposable cartridges that have a floss pad surrounding them. This pad is primarily for mechanical filtration but will also house nitrifying bacteria. The drawback to this as a primary biological filter is when you dispose of the cartridge, you dispose of the bacteria colony as well.

Advanced power filters include a separate area for biological media. These are usually in the form of a compartment in the filter filled with biological media or an attached external ‘bio wheel’, a pleated wheel that the water flows over as it is leaving the filter and returning to the aquarium.

Wet/Dry Filters

Wet/Dry Filters provide the ultimate in biological filtration. They are great for saltwater fish-only aquariums or any large aquarium setup that demands excellent biological filtration. Custom sumps are an example of wet/dry filter. Usually, sump pumps are installed in specially constructed sump pits. Water flows into the sump pit through drains or by natural water migration through the soil. The sump pump’s job is to pump the water out of the pit and away from the building so the basement or crawlspace stays dry.

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