Aquarium Fish Tank

Fish Tank Filter Types


Types of Filter

Canister Filters

These are external fish tank filters.  The ideal solution for maintaining a large aquarium.  As beginners usually start of with smaller tanks these may not be the first choice for many new aquarists.

A canister filter is a self-contained fish tank filter, they hold different types of media for filtration - mechanical, biological, or chemical filter media. Each of which has a particular purpose.

Canister filters are used in freshwater tanks, saltwater tanks, reef tanks, as well as turtle tanks.

External filters can contain a greater amount of sponge and biological media than any that sit in the tank, enhancing the level of mechanical filtration and breakdown of ammonia.  They are also good for reducing nitrate levels.  See ‘Nitrates can kill fish’ here.

Canister filters have an integral water pump.

Canister filters have many different features and each manufacturer will tell you how good their new model is compared to anything else. 

Key features to consider are the initial cost, the running cost, the noise of the filter (this may be a surprise to new fish keepers - there can be a very notable difference and a noise filter will really start to annoy you after a while), the types of media that it can hold, how often it needs to be changed and the how much maintenance they need.

Some great brands include EHEIM, Fluval, Hydor and SunSun.

Box Filters

The box filter is a simple filter and works really efficiently for small aquariums and fish bowls. One box filter is perfect for your 10 gallon (or smaller) tank.  They are plastic boxes with a perforated lid and a lift tube.

The lift tube connects to an air hose, and the bubbles rise up the tube from the bottom of the box. Filtration media is packed around the tube, to fill the box.  Water flows down through the media and up the tube, drawn by the rising stream of air bubbles.  The bubbles help to aerate and oxygenate your tank. 

These require an air pump and airline tubing to operate, usually they are not included.  Check if sold separately or included if you are buying a box filter bundle.

Easy to assemble and to use.  Little can go wrong with these - no moving parts.

This filter is excellent for small size fish like dwarf cichlid, guppy, killifish, shrimp etc., or for hatcheries, maternity, nano tanks, and fry tanks, as the filter produces minimal current and has almost no way to suck the fish through the filter.

Outside Filters

Very common today is the hang-on-back (HOB) filter. These filters hang on the back of your aquarium, and provide excellent mechanical and biological filtration. They are ideal for use in tanks where space is limited inside the tank, and remove the need for unsightly filters in the tank itself. 

They use a pump to suck water up a supply tube from the aquarium. The water then flows through a series of compartments with various media and back into the tank via an overflow.

Note, unlike the box filter with a narrow tube these filters have a wider intake tube and the intake strainer may not stop small fish such as neon tetra size being sucked into the filter.  We recommend for smaller fish that you add a pre-filter sponge to stop this happening.

These filters are available in a full range of sizes. A simple guide is to select a filter with a flow rate at least six times the volume of the tank—so for a 30-gallon tank you want a flow rate of about 200 gph (gallons per hour).

Very popular are the AquaClear, Finnex PX and Tetra Filters.

Trickle Filters

Trickle or wet-dry filters drip or spray aquarium water over a medium for marine and freshwater aquariums. This maximizes oxygen saturation and provides excellent biofiltration.  The filter box is placed on top of the aquarium.

Water is pumped over a number of perforated trays containing filter wool or some other filter material. The water trickles through the trays, keeping the filter wool wet but not completely submerged, allowing aerobic bacteria to grow and aiding biological filtration. The water returns to the aquarium like rain.

The water trickles through the biological filter media drawn downward toward the sump by gravity. As the water flows down through the media, it is exposed to free-moving air, which keeps the water oxygen rich. The high oxygen levels in the water in the tower improves the efficiency of the nitrifying bacteria providing biological filtration.

These units are extremely efficient at converting ammonia to nitrate. They provide a large surface area for beneficial bacteria colonies to grow.  They are also known as nitrate factories – avoiding nitrate build up is extremely important.

Trickle filters provide excellent biological filtration.  Some trickle filters are fitted with mechanical and/or chemical filtration cartridges in the sump so the water has to flow through this additional filter media before being returned to the fish tank.

Fluidized Bed Filters or Chemical Reactors

A fluidized bed filter is a container that hangs on the back of your fish tank or sits in a sump.  It can also be a cylinder or even a canister which can sit in a sump on the floor beside or under your fish tank.  This will be connected to a pump to push water through the filter.

These filters are actually known by many terms and if you are searching for one online then try one or all of the following terms to get the best results:

  • Aquarium reactor
  • Biopellet reactor
  • Calcium reactor
  • Carbon reactor
  • CO2 reactor
  • Chemical reactor
  • Fluidized Bed Filter
  • Media reactor
  • Phosban reactpr
  • Phosphate reactor
  • Suspended particulate filter
  • Suspended sand filter

These filters are chambers in which aquarium water ‘reacts’ with some medium to alter the water chemistry, either adding substances to the water or removing them.  As long as it is a chemical reaction, and the medium is freely mixing with the water, the device is called a reactor.   This versatile reactor can be used with phosphate resins, phosphate sponges, activated carbon, nitrate sponges, and other resin filter media.

These filters are designed to optimize the contact time between the water and the surface area of the reactor media. They take full advantage of the entire capacity of the media.

Protein Skimmers - saltwater aquariums

Protein skimmers are used in saltwater setups to remove dissolved substances before they begin to break down. Some models stand alone (or hang on the tank) with their own water pumps, and others are designed to operate in a sump, utilizing the sump’s plumbing and pump.

The life of a saltwater aquarium ecosystem is dependent on choosing the right protein skimmer. Protein skimmers remove organic compounds, such as food, waste, and other materials from the water of your tank.

Water is pumped through a tall vertical column in which air bubbles are rising. The air can be supplied by an air pump or by a water pump with venturi, which is a valve that draws air into the water stream. The basic principle here is to get air bubbles into prolonged contact with the tank water. Polluting substances are attracted to the air-water interface of an air bubble. These concentrate in the bubble stream, rising with it and appearing at the top as foam. The foam continues to rise into a collection apparatus/cup, while the water flows back into the tank. Once the organic waste is condensed by the air-bubbles, they cannot dissolve back into the water, making it easy to remove the waste through mechanical filtration methods.

These are simple to set-up, easy to clean.  Available for nano tanks upwards. Seen as having good energy efficiency, delivering very effective organic waste removal.

UV Sterilizers

Rather than removing or adding substances/chemicals, an ultraviolet (UV) sterilizer kills living organisms. Tank water is circulated through a chamber exposed to UV radiation from a special bulb. The longer the water is in contact with the UV radiation, the better.  The submersible UV sterilizer allows simple and effective UV control of harmful microorganisms & free-floating algae.

UV sterilizers are indiscriminate—they kill all living organisms, from algae cells to pathogens. Thus, they are widely used to control disease.

For use in fresh or saltwater aquariums and garden ponds.  When properly matched to the aquarium size they can destroy any free-swimming pathogens or parasites. In pond setups they are often used to control greenwater algae blooms.   

To be effective you must change bulb yearly for optimum UV performance.  Never expose the UV bulb as it is dangerous to you and your fish.  It will kill your fish and can cause cancer in people - this is why it is an enclosed bulb.