Aquarium filter

[1][2][3] Aquarium filters remove physical and soluble chemical waste products from aquaria, simplifying maintenance.

Furthermore, aquarium filters are necessary to support life as aquaria are relatively small, closed volumes of water compared to the natural environment of most fish.

The bacteria responsible for breaking down the ammonia by converting it to nitrite, Nitrosomonas, colonize the surface of any objects inside the aquarium.

[5] In most cases, a biological filter is nothing more than a chemically inert porous sponge, which provides a greatly enlarged surface area on which these bacteria can develop.

These bacterial colonies take several weeks to form, during which time the aquarium is vulnerable to a condition commonly known as "new tank syndrome" if stocked with fish too quickly.

[6] Accumulation of toxic ammonia from decomposing wastes is the largest cause of fish mortality in new, poorly maintained, or overloaded aquariums.

Mechanical filtration is typically achieved by passing water through materials which act as a sieve, physically trapping the particulate matter.

[1] Removal of solid waste can be as simple as physical hand netting of debris, and/or involve highly complex equipment.

All removal of solid wastes involve filtering water through some form of mesh in a process known as mechanical filtration.

Mechanical filtration is ultimately ineffective if the solid wastes are not removed from the filter, and are allowed to decay and dissolve in the water.

Several techniques, collectively known as chemical filtration, are used for the removal of dissolved wastes, the most popular being the use of activated carbon and foam fractionation.

Synthetic sponges or foams, various ceramic and sintered glass and silicon products along with igneous gravels are also used as mechanical filter materials.

These highly porous materials act as adsorbates binding various chemicals to their large external surfaces[2] and also as sites of bacterial colonisation.

The filter wool traps large debris and particles, and the activated carbon adsorbs smaller impurities.

[9] This is particularly important in the case of activated carbon filters, which may re-release their adsorbed contents in large (and therefore harmful) doses if they are allowed to saturate.

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.

Also, as a filter with external plumbing, it supports in-line installation of other aquarium equipment, such as water heaters and carbon dioxide diffusers.

The water trickles through the trays, keeping the filter wool wet but not completely submerged, allowing aerobic bacteria to grow and aiding biological filtration.

This may be a filter wool/plastic grid rolled into a circular shape (DLS or "Double Layer Spiral") or any number of plastic media commonly known as Bio Balls.

As the water cascades over the media, CO2 is given off, oxygen is picked up, and bacteria convert the waste from the tank into less harmful materials.

[18] Algae and disease-causing organisms can also be removed by treating the water with ultraviolet irradiation, but the drawback of UV is that it will kill beneficial bacteria as well.

In its simplest DIY internal version an FBF is very easy to build, with a container, sand, pump, and some plumbing.

Both generally work by airlift, using bubbles from an air pump rising in a tube to create flow.

Water enters slits in the box, passes through a layer of medium, then exits through the airlift tube to return to the aquarium.