Keeping your aquarium water clear and clean is the goal of every aquarist. Canister aquarium filters are designed to provide superior filtration for just about any size aquarium.
The ability to use a variety of filtration media types coupled with a high volume flow rate equals a powerful water purification system.
Aquarium canister filters come with a variety of features suitable for freshwater and saltwater aquariums.
We’ll outline the most important features to look for in the best aquarium canister filters for this year.
How aquarium canister filters work
The basic function of the canister filter is to pass aquarium water through several layers of filtration media. The end goal being to remove pollutants by capturing them on the filter media.
The filter media is contained in the canister or “tank” of the filter. Using hoses, water flows by gravity out of the aquarium and into the canister.
A water pump, typically mounted in the lid of the canister, pumps filtered water back into the aquarium. The lid is sealed to the canister with an O-ring. Clamps hold the lid onto the canister tank.
The best aquarium canister filters come with a set of shut-off valves that make changing the filter media much easier. Canister filter varies in canister size and the flow rate the water pump produces.
Canister filter manufacturers often match up recommended aquarium sizes to each filter model.
The three stages of aquarium filtration
There are three categories, or stages, of aquarium filtration.
Mechanical filtration relates to screening out solid particles that are suspended in the aquarium water. These particles include bits of uneaten fish food, dust from new aquarium gravel, very fine marine sediments (saltwater fish and reef aquariums), plant fragments and tiny single-celled algae that cause “green water” blooms.
Mechanical filtration is the first stage of filtration in the canister filter. The idea is to capture the “dirt” first so the other filtration materials remain free of debris.
Activated carbon, for example, captures organic chemicals inside tiny pores. If the pores get clogged with dirt the activated carbon can’t do its job.
Foam pads are the most common form of mechanical filtration filter media used in canister filters. The best canister filters use several layers of foam pads, each with a different porosity. The idea is to use a large pore sponge first, to screen out the larger particles. The next foam pad should have a much finer pore size.
Fine porosity sponge pads capture the smaller suspended particles like algae cells and tiny pieces of organic matter. Sponge filter pads can be rinsed and reused several times.
If the sponge pads are not cleaned every few weeks, they clog with decaying organic matter and reduce the water flow rate through the canister filter.
The decaying organic matter also releases algae-promoting nutrients into the aquarium water. Mechanical filter media is available in several forms:
- Pre-cut foams discs specific to the canister filter model
- Cut-to-fit foam pads
- Cut-to-fit filter pads
Chemical filter media
Chemical filter media removes pollutants like ammonia, nitrite and nitrate and other dissolved waste substances from the aquarium water.
Dissolved substances (chemicals) are usually invisible. Ammonia, for example, is released by fish and invertebrates as a waste product. It is colorless and odorless yet highly toxic to aquatic life.Dissolved organic compounds cause a yellowish tint to aquarium water.
There are many types of chemical filtration media for aquariums. Some can be used in freshwater and marine tanks while others only work in freshwater aquariums.
Granular activated carbon adsorbs dissolved organic pollutants from freshwater and saltwater. Organic pollutants cause yellowish water discoloration, odors and can increase the chances of fish disease problems.
Activated carbon has a microscopic network of tiny pores that adsorb organic chemicals and trap them inside the porous network.
Phosphate removers specifically remove inorganic phosphate from aquarium water. Phosphate is an algae-promoting nutrient that builds up naturally in all aquariums. Decomposing fish waste and uneaten bits of fish food release phosphate into the water, stimulating algae growth in the water, on the gravel and aquarium glass.
Ammonia removers, made from a natural mineral called zeolite, only work in freshwater aquariums. The granular material has a high attraction for ammonia fish waste and will help protect fish from ammonia poisoning. Zeolite ammonia removers won’t work in saltwater due to the high sodium level in the sea water.
Biological filtration refers to the process of biologically converting toxic ammonia waste into nitrite (also toxic) and then to relatively harmless nitrate. This natural process is performed by beneficial “nitrifying” bacteria. These bacteria like to attach to solid surfaces and form colonies.
Biological filtration media provide a safe haven for these bacteria inside the canister filter. As water flows through the “bio-media” the bacteria convert the toxins to nitrate. Biological filter media comes in several forms:
- Porous ceramic rings
- Plastic balls and rings
- Porous beads
- Pieces of porous foam
Some aquarium canister filter brands come with one or two types of filter media.
When the filter media needs to be replaced you’ll have to cut your own filter pads and find other media that fit in the canister. Good aquarium canister filters make replacement filter media designed to fit perfectly into your model. Look for filter media that is conveniently bagged in flow-through pouches.
Basic canister filters instruct you to simply “drop in” the un-bagged filter media into the canister. The media is arranged so water first passes through the mechanical filter stage, then the chemical filtration stage and finally the biological filtration media. This is referred to as a three-stage canister filter.
Granular filtration media, like activated carbon, may come packaged in a flow-through pouch. Some aquarists like to buy their filter media in bulk and pour it into their own filter bags. This gives the option to use any kind of filter media in your canister filter.
The best canister filters come with individual media baskets. The baskets hold the filtration media and are “loaded” or stacked into the canister filter. Media baskets make it easier to arrange the media and rinse and replace new media. Some canister filters have an extra basket or fourth stage, allowing you to add extra filtration media.
More advanced aquarium canister filters have an ultraviolet light built into the canister. The UV light kills algae cells along with bacteria and parasites that cause fish health problems. The UV light won’t sterilize the water but it will reduce the population of undesirable microbes. UV lights are especially helpful in reducing algae problems in freshwater and marine aquariums.
Important things to look for when selecting a canister filter
- Canister filter flow rates are measured with no filter media in the canister and with least amount of resistance to flow. Under real-world conditions, the actual flow rates will be less than stated on the package. You may want to consider upsizing to the next model.
- The best-rated canister filters have long hoses. This makes it easier to run the hoses under the aquarium and to the canister filter.
- Most good canister filters have sturdy clamps that hold the lid securely onto the canister tank. Flimsy clamps break easily and allow for water leaks.
- Look for a canister filter that has high-quality quick disconnect valves. The valves allow the canister to be disconnected from the hoses and taken to a sink for cleaning.
Top 8 Aquarium Canister Filters
The Fluval 07 series of external canister filters marks the seventh update since the Fluval line was created.
Improvements include a high-quality Italian pump motor for long, trouble-free life.
A diamond-polished ceramic (alumina) impeller shaft, coupled with liquid crystal polymer rotor dampens vibrations within the pump assembly.
The plastic impeller cover is co-molded with a soft polymer for a tight seal and stable pump shaft alignment. Although you probably won’t see it, the pump’s internal support structure has been re-designed to eliminate annoying rattles and humming noises. The canister tank is supported by large vibration-adsorbing rubber feet.
The 07 series also include re-designed filter baskets for easy removal and media changes. You don’t have to empty the canister tank of water to change the media! The filter priming system has been beefed-up to make it stronger and easier to pump.
- All models come complete with filter media.
- Stronger priming pump.
- Super-quiet motor.
- Silent vibration-free operation.
- White hose fittings don’t blend into the aquascape.
- Hoses are flimsy.
- No spray bar.
The Hydor Professional canister filter series uses a high-quality ceramic shaft on the pump motor.
The impeller, which pumps the water, rotates on the ceramic shaft.
A ceramic shaft ensures smooth, quiet operation of the water pump. The long hoses make it easy to connect the filter and avoid kinking.
The canister comes with individual media baskets complete with mechanical filter pads and biological filtration media.
The Hydor Professional series includes a spray bar attachment. The spray bar tube has a series of holes that spray water across the surface of the water. This provides aeration for the fish. The intake and spray bar tubing and fittings are mounted inside the aquarium with suction cups.
One feature not found on all aquarium canister filters is a priming system. Without a priming system, you’ll have to start the siphon into the canister by sucking on the end of the outlet hose. It’s different with the Hydor.
Simply pump the primer knob and water automatically fills the canister, pushing air out of the canister tank. This makes filter start-up quick and easy. The quick disconnect valves use ball-type mechanisms for smooth, leak-free action.
The Hydor Professional canister filter line does not include activated carbon.
You’ll have to purchase Hydor activated carbon separately.
The Hydor Professional is available in five aquarium-rated sizes - 20-40 gallons, 40-75 gallons, 60-100 gallons, 75-125 gallons and 90-150 gallons. Pump flow rates range from 160 to 290 gallons per hour, depending on the model.
- Hydor Professional series is available for a variety of aquarium sizes.
- Uses a ceramic pump shaft for quiet operation.
- Has filter media baskets.
- Easy priming system.
- Does not come with activated carbon.
- Replacement parts are expensive.
Both filters share the basket-in-a-basket design.
The round media baskets stack on top of one another like other canister filters but there is a difference.
The Fluval FX baskets have an outer basket and an inner basket. Multiple baskets stack and nest together.
With the FX design, the water path follows
The FX4 has five stages of filtration and the FX6 has six filtration stages.
The filtration media consist of FX pads that capture large particles and debris for effective mechanical filtration, the crucial first stage in the filtration process.
Bio-Foam pads trap fine particles and act as a biological filter media. Biomax biological filter rings are hard, ceramic media with a complex pore system for beneficial bacteria. Carbon impregnated foam pads are pre-cut for Fluval FX canister filters. The carbon impregnated pads capture micro particles, odors, discoloration and organic contaminants.
The Smart Pump technology automatically primes the canister filter. The smart digital pump monitoring system automatically adjusts the pump speed to maintain a consistent flow rate and even purges the canister of trapped air every 12 hours. The Aqua Stop disconnect valves make it easy to change the canister.
The FX4 is rated for aquariums up to 250 gallons and has an actual maximum flow rate of 450 gallons per hour.
The FX6 is rated for aquariums up to 400 gallons and has an actual flow rate of 563 gallons per hour.
- High-quality construction.
- Large sturdy quick disconnect valves.
- Additional Fluval filter media can be used.
- Multi-directional output nozzle.
- Large canister holds plenty of filter media.
- Made in Italy.
- Higher initial cost to purchase than other filters.
- Takes up a lot of space.
- Maintenance is complicated due to basket design.
The BioMaster Thermo canister filters is a combination German engineering and Italian pump know-how.
The Thermo series canisters are designed with an internal heater. The idea is to free up more space in the aquarium and hide the heater from view.
BioMaster canisters have a removable pre-filter module designed to be easily removed, cleaned and replaced without the need to open up the canister. The prefilter module simply twists out of the canister. The prefilter media is rinsed and reused again.
Shut-off levers are built into the canister lid, making it easy to disconnect the filter from the aquarium.
Accessories include intake and outlet, suction cups and a spray bar. The filters come complete with prefilter, activated carbon pads and bio media.
There are three models to choose from: 250 (up to 70 US gal), 350 (up to 90 US gal) and 600 (up to 150 US Gal).
- Attractive design.
- Quiet operation.
- Easy to maintain.
- Built-in priming pump.
- Air build-up inside the canister sends bursts of bubbles into the aquarium.
- OASE acknowledges design problem and is working on an update.
5. API Filstar
The API Filstar line features a patented quick disconnect valve that shuts off both hoses and disconnects from the canister with the flip of a lever.
This makes it quick and easy to carry the canister to the sink for cleaning.
The Filstar canister filter used heavy-duty baskets to hold filtration media.
The filters come with two kinds of foam pads for mechanical filtration.
The coarse foam has a rating of 20 pores per inch to capture large particles. The fine foam pad is rated at 30 pores per inch and captures cloud-causing particulates and algae. The filter also includes Bio-Chem Zorb.
Bio-Chem Zorb is a blend of premium activated carbon and high-performance adsorption resins in a ready to use pouch. Bio-Chem Zorb is an advanced chemical filtration media that keeps aquarium water free of harmful organics.
Also included with the canister filter is biological media called Bio-Chem Stars. Bio-Chem Stars are made of porous plastic specifically made for biological filtration.
The star-shaped media have 50-micron pores, providing protective growing areas for beneficial nitrifying bacteria.
As a bonus, the Filstar comes with a polishing filter pad that makes the water sparkling clear. The canister filter comes complete with six-foot-long hoses and high-quality inlet and outlet fittings.
There are many types of replacement filtration media available including Nitra-Zorb. Nitra-Zorb removes algae-stimulating nitrate from the aquarium water.
- Comes complete with all the necessary filtration media.
- Quiet operation.
- Easy to change the filtration media.
- Long hoses.
- Replacement media comes in ready to use pouches.
- Aquarium size recommendations are slightly exaggerated.
- Does not come with a spray bar.
- Does not have a self-priming feature.
Eheim is famous for high-quality German-engineered aquarium filters.
The Eheim Classic series is a no-frills aquarium canister filter with only basic features.
The Eheim Classic canister filters do not have media baskets. Filtration material is placed directly inside the canister.
Eheim MECH is a loose mechanical filter media designed to trap debris.
A foam pad is placed on top of the MECH to hold it in place.
The Classic canister line also comes with Eheim SubstratPro, a loose biological media for nitrifying bacteria.
Eheim Classic aquarium canister filters do not come with activated carbon. Eheim activated carbon filter pads are available separately. Loose activated carbon can be poured into a filter bag and placed in the canister if desired.
Cleaning of the filtration media will require collecting the loose MECH and SubstratPro in separate containers for cleaning. This will lengthen the time it takes to service the canister filter. Included with the canister filter is a set of flexible hoses, spray bar, an inlet pipe and suction cups.
Eheim Classic canister filters come with two-piece valves that disconnect for easy filter clean-outs.
The Eheim Classic filter line is rated for aquariums at 40 gallons, 66 gallons, and 92 gallons.
- High-quality plastic components.
- Reliable water pump.
- Quiet operation.
- Limited aquarium sizes.
- Does not include activated carbon.
- MECH and SubstratPro do not come in a filter bag.
- Complicated to service the canister filter with loose media.
All Penn Plax Cascade canister filters have plastic media baskets that stack inside the canister.
The Cascade canister filters come in three sizes and are rated for 30 gallons, 65 gallons and 150 gallons.
Penn Plax Cascade filter media consists of sponge pads for trapping debris.
The coarse sponge also supports biological filtration by providing surface area for nitrifying bacterial growth. Ceramic biological filtration rings are supplied in a flow-through pouch. Granular activated carbon is also included in a flow-through pouch.
Changing the filter media is quick and easy. The
Canister filters can flush floating food flakes down into the water and get sucked into the filter. Delicate fish sometimes have a difficult time getting food if the water flow is too strong.
The valves can provide a temporary flow reduction while fish are being fed.
The Penn Plax Cascade line feature a one-push priming button on top of the canister. Simply push the button to start the siphon and fill the canister with water.
Four heavy duty locking clamps secure the upper pump house to the canister.
Replacement filter media is available.
The Cascade canister filter comes with all the necessary filter media along with long tubing, inlet and outlets, suction cups and a spray bar.
The Cascade have a three-year warranty.
- Comes will all necessary filter media.
- Three-year warranty.
- Quick disconnect valves can also reduce flow rate.
- Poor customer service.
- Tubing is somewhat stiff and inflexible.
- Quality control is poor, some units leak.
The Sunsun 4-Stage Canister filter has three filter baskets for holding filtration materials like activated carbon, biological filtration media and foam pads.
The Sunsun 4-Stage Canister Filter comes only with fine and coarse filter pads.
Sunsun offers activated carbon in a flow-through pouch.
One-pound of porous ceramic rings are also available in a filter pouch.
Sunsun plastic biological filtration balls are yet another option when outfitting your canister filter. These can be purchased separately or as a complete kit. The replacement filter media kits offer an economical alternative to purchasing individual filtration media.
The Sunsun is designed with a priming button. Simply press the priming button to fill the canister with water. Then, plug it in and the filter begins pumping immediately.
The priming feature eliminates the need for siphon priming.
The fourth stage of the Sunsun canister filter is a built-in 9-watt ultraviolet (UV) light.
The UV light kills suspended algae that pass through the filter.
When exposed to ultraviolet light the algae cells are killed. This will reduce the chances of an algae bloom and keep the aquarium clear.
The UV light feature also helps reduce pathogenic bacteria and parasites the cause fish diseases. The disinfection properties of UV lights is reduced when the water is dirty.
The dirt particles block the UV rays from striking the microbes and reduce the effectiveness.
The canister includes long hoses, spray
- Rated for up to 150 gallons.
- Uses UV light to reduce algae and pathogens.
- Bulk replacement filter media is available.
- Does not come with activated carbon.
- Does not come with biological filter media.
The new Fluval 07 series offers quite a few advancements in the pump and motor design. They’re mostly “hidden” inside the motor but these design changes will pay off with a super-quiet filter and much more reliable water pump. This translates into a trouble-free canister filter that is a joy to own.
The 07 series also use a new filter basket design that lets you change the media without the need to drain the canister. This is handy if you’re in a rush and just want to quickly swap out old media. Another nice feature is the true flow rates are provided rather than the unrealistic “ideal” maximum flow rates based on only the pump and not a canister filled with filter media.
The API Filstar canister filters are built with thick high-quality plastic components that will hold up over time. This is important as inexpensive thin plastic components can deform over time and cause leaks.
The Filstar canisters use a unique “figure eight” O-ring that forms an especially tight water seal. This ensures the filter primes easily and keeps running with no leaks.
Unlike the Eheim filters, Filstar canisters come with stackable media baskets that allow you to add large amounts of biological filter media, activated carbon and more.
The Filstar canister filters come with premium filtration media. You don’t need to buy anything else to set up the filter. There are also a variety of ready-to-use API filter media available in flow-through pouches.
The Filstar pump motors run silently and are reliable. The Filstar canister filters are available in four sizes for just about any aquarium. Replacement parts are readily available.
The BioMaster design looks impressive but the issue of air building up inside the canister is a concern. I recommend avoiding this series until the bugs are worked out.
The Hydor Professional canister filters are also a top choice. The Hydor professional line, like the Filstar, come with stackable media baskets. The Hydor Professional canisters come with a spray bar. Filstar canister filters have an outlet nozzle but no spray bar. The Hydor Professional also has the automatic priming feature that makes starting up the filter easier.
The UV light feature of the Sunsun canister filter is appealing but is not necessary for every aquarium. It also adds a layer of complexity to the filter and uses more energy.
The Fluval FX series offers the largest canister of the group. The digital motor control and variety of filtration stages makes the FX aquarium canister filters a tech-lovers dream.
While the FX series is more complicated to assemble and maintain, it is a complete filtration package that provides all the necessary features to keep an aquarium well-filtered.
Another nice feature is the true flow rates are provided rather than the unrealistic “ideal” maximum flow rates based on only the pump and not a canister filled with filter media.
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