The main purpose of fish tank filters is to remove dangerous chemicals, excess food, decaying organic matter, and the waste products of fish. Fish constantly excrete waste while swimming around. If the waste is not removed at proper intervals, then the toxins from the tank will build up to high concentrations which may poison the fish.

The best types of aquarium filters today such as power (HOB), canister, internal, corner (box), sponge filters… are all useful if you know what fish tank types they are intended for. For choosing the right filter for fish tank, firstly you should understand the mechanism behind these filters and how do they work? In this article, I will outline some of the most popular aquarium filter types to help you know which is the best one for your fish tank.

Firstly, you should acquire some knowledge about three types of filtration that are used by most aquarium filters today.

3 types of filtration mechanical, biological and chemical

Aquarium filters clean the fish tank by using chemical/biological/mechanical means (or filter media) they respectively correspond to chemical/biological/mechanical filtration.


The filtration system of a canister filter

Mechanical filtration (media: sponge/foam, floss, pre-filter media…) is to trap solid matters for manual removal every cleaning the filter. The mechanical filtration keeps the water free of floating wastes and helps to prevent the filter clot during operating.

Biological filtration (media: ceramic rings, bio-sponge, bio-foam…) is to provide a house for denitrifying bacteria to build up. These helpful bacteria help to degrade nitrogenous toxins (ammonia – NH3 and nitrite – NO2) resulting from the decomposition of fish waste and left uneaten food. Biological filtration is the most important stage which provides a safe and clean environment for your fish and invertebrates.

Chemical filtration (media: activated carbon/charcoal) is to remove heavy metals, chlorine, dissolved proteins, and carbohydrates that leaves your aquarium nothing more than a clean and clear water. Some chemical filter media can remove dissolved organic compounds such as phosphates and nitrates which are well-known to contribute to the yellowish water and the outgrow of algae.

Each of them has respective mechanism but they help each other (mechanical filtration reduces the load on biological filtration and chemical filtration deals with what was left after biological stage). The best filtration system is one that can provide an ideal environment for all of these filtration types to work together to completely purify the aquarium water.

Power filters (HOB filter) – for 10-70 gallon tanks

Power filter, also called as Hang on Back (HOB) filter or external power filter, is a very popular external aquarium filter type on the market today because it is very powerful (only after canister filters) and costs a very affordable price. Power filters are very popular because they are cheaper than canister filters and can keep the water clean in a broad range of tank sizes from 10 to 70 gallons.

Best power filterBest power filter

The power filter is hung on the side of the fish tank (hence its name Hang On Back) and does all its filtration outside the tank. Water is sucked into the intake tube, then it travels through a series of filter media inside the filter chamber including filter media that perform many stages of filtration (biological, mechanical and chemical) before it flows back to the aquarium from the top.

  • Carry greater quantity of filter materials for the efficient filtration
  • Not take more space inside the aquarium
  • Larger filter chamber for less maintenance
  • Clear up cloudy water pretty quick
  • Cheaper than canister filters and is a great replacement for these luxury filters.
  • Little expensive than other filters
  • Some can’t auto prime by themselves and need your help to get starting.

AquaClear series – best power filters for 5-110 gallon tanks

AquaClear power filters are the best power filters on the market. I love these filters most in this article. They feature a very large filter chamber for the best filtration, free to use filter materials, less and lower cost maintenance. Cycle Guard with BioMax included in a patented Re-filtration system makes the biological filtration to be excellently performed to keep your fish happy and healthy. The filters come in various sizes available for different aquarium sizes for you to choose.

Marineland Penguin bio-wheel power filters for tanks up to 70 gallons

  • Marineland Penguin power filter with Bio-WheelEditor's rating: Check on
  • Marineland Penguin 100 (FR: 100 GPH) is rated for aquariums up to 20 gallons.
  • Marineland Penguin 150 (FR: 150 GPH) for 20 – 30 gallon tanks.
  • Marineland Penguin 200 (FR: 200 GPH) for 30 – 50 gallon tanks.
  • Marineland Penguin 350 (FR: 350 GPH) for 50 – 70 gallon tanks.

Marineland Penguin power filters feature a great built-in Bio-Wheel system for the superior performance of biological filtration. Whereby, the aquarium water is free of nitrogenous toxins and safe for your aquarium’s inhabitants. The Marineland Penguin power filters are available in various sizes for aquariums from 20 to 70 gallons.

Find other options for an external power filter :

Internal filters (Internal power filter) – for 10-40 gallon tanks

Internal filter also called as internal power filter, is a filter which is installed and do its works within the aquarium. Internal power filter is similar to external power filter but is meant to be submerged inside aquarium. They also tend to be smaller than external power filters, meaning even smaller media chambers.

Best internal filterBest internal filter

Because these filters are placed and work inside the aquariums, they are limited in the size as well as the filter capacity. Therefore, internal filters can only fit for small to medium tank sizes. These filters are popular for low water habitats like turtle tanks. They are also sometimes used to supplement canister filters or external power filters in larger tanks, but their visibility within the tank often makes them less than ideal.

  • Good for a small to medium size aquarium
  • Cheaper than external power and canister filters
  • Ideal filters for small aquariums
  • Can be used on reptile turtle tanks with low water level.
  • Take space inside the aquarium
  • Small capacity, some can contain only mechanical filter media
  • Not strong enough for a large fish tank.

Aqueon QuietFlow – best internal filters for tanks up to 40 gallons

  • Aqueon QuietFlow internal filtersEditor's rating: Check on
  • Aqueon QuietFlow mini has a flow rate of 57 GPH (gallons per hour) ideal for 10 gallon fish tanks.
  • Aqueon QuietFlow small (FR: 66 GPH) for 15 gallon fish tanks.
  • Aqueon QuietFlow medium (FR: 142 GPH) for 30 gallon fish tanks.
  • Aqueon QuietFlow large (FR: 155 GPH) for 40 gallon fish tanks.

I recommend these internal filters because its capacity is large enough to accommodate some biological filter media that other internal filters can’t do. The flow rate and direction of the water output can be adjustable that makes this internal filter ideal for smaller tanks with small fish. If you love to use a traditional internal filter, Aqueon QuietFlow internal filters are the best and cheapest ones to buy. They come in various sizes for aquariums up to 40 gallons.

Fluval U series – best internal filters for tanks up to 65 gallons

  • Fluval U series underwater filterEditor's rating: Check on
  • Fluval U1 is ideal for tanks up to 15 gallons
  • Fluval U2 is ideal for tanks from 12 to 30 gallons
  • Fluval U3 is ideal for tanks from 24 to 40 gallons
  • Fluval U4 is ideal for tanks from 34 to 65 gallons

Fluval U series underwater filters are designed to be safely applied on freshwater, marine or reptile turtle tanks. I love these filters because their internal chamber is more larger than other internal filters that offers the flexibility in use filter media. While most internal filters can use only one cartridge which usually contains two types filter media (floss pads and activated carbon), the internal capacity of Fluval U series is large enough to accommodate some Biomax (ceramide rings) to perform the best biological filtration. The setup and maintenance of this model are also simple because there is a flip-top lid allowing for quick and easy access to filter media for cleaning or changing.

Canister filters – best for medium to extra-large fish tanks

Canister filters are an external pressurized filter for larger aquariums, upwards of 30-50 gallons. They can be set up underneath or next to your tank, so they’re not as limited in size as power filters. Because their capacity is much more larger than power or internal filters, they are the best at all 3 types of filtration (mechanical, chemical and biological). If you have a large fish tank or your aquarium is overload, you should have a canister filter.

Best canister filtersBest canister filters
  • Excellent performance of mechanical, chemical, and biological filtration
  • Carry greater quantity of filtering materials for less maintenance
  • Need very little maintenance and does an excellent job at keeping your fish tank water clear and clean
  • Ideal fish tank filter for busy people who can’t find more time to clean their aquariums regularly.
  • They are expensive so you should consider a canister filter only if you have a large tank
  • They are much larger than other filters so they need more space to place.

Read more about canister filters:

Fluval 06 series – best canister filters for tanks up to 100 gallons

  • Best canister external filtersEditor's rating: Check on
  • Fluval 06 series are the best and quietest filters for aquariums up to 100 gallons.
  • Fluval 106 (FR: 145 GPH) for aquarium up to 25 gallons.
  • Fluval 206 (FR: 206 GPH) for aquarium up to 45 gallons.
  • Fluval 306 (FR: 303 GPH) for aquarium up to 70 gallons.
  • Fluval 406 (FR: 383 GPH) for aquarium up to 100 gallons.

The Hagen Fluval 06 series own many powerful and unique features making them the best canister filters on the aquatic hobby. The most advanced features can be mentioned are the durable construction of the filter, quiet operation, easy setup, quick and easy maintenance without water leaks and mess.

Read the full review of Fluval 06 series:

Plax Cascade series canisters for aquariums up to 200 gallons

  • Penn Plax Cascade series canisterEditor's rating: Check on
  • Plax Cascade series canisters are the most cheapest and reliable canister filters.
  • Cascade 500 (FR: 115 GPH) for aquariums up to 30 gallons.
  • Cascade 700 (FR: 185 GPH) for aquariums up to 65 gallons.
  • Cascade 1000 (FR: 265 GPH) for aquariums up to 100 gallons.
  • Cascade 1200 (FR: 315 GPH) for aquariums up to 150 gallons.
  • Cascade 1500 (FR: 350 GPH) for aquariums up to 200 gallons.

Plax Cascade series canister filters are so powerful and durable like the Fluval 06 series; however, they are cheaper than the Fluval 06 series that makes them popular in the aquatic hobby. These filters are very efficient in keeping your aquarium water clean and clear for a long period with only a little maintenance. They come with many filter media brackets and large filter capacity for accommodating more filter media and performing the most biological filtration.

Read the full review of Plax Cascade series:

Fluval FX4/FX6 canister filters for large tanks up to 250/400 gallons

If you have a fish tank that hold over 200 gallons of water, you should consider a Fluval FX4 or FX6 canister filter. They are external filters designed to keep very large fish tanks clean and clear for a long time with less maintenance. They are a great choice for busy people who don’t have many time to clean the filter. Like other products from Fluval, these external filters are well constructed and very easy to set up, they are also designed to be convenient in use and maintenance for the users.

Read the full review of Fluval FX4/FX6:

Corner filters (internal box filters) – for small tanks

Corner filter is a smaller plastic box filter which sits on the bottom of the fish tank, above the gravel in a corner of the fish tank. The box contains layers of filter media (floss, ceramide rings, gravel, charcoal…) through which water is sucked through and filtered before exiting from the top.

corner fish tank filter

It works basing on an aquarium air pump (usually buy separately) that push air into the filter, and then the air escape out of the filter making a force sucking the aquarium water into the filter media to perform the mechanical filtration. The air pump provides aeration for fish as well as for helpful bacteria colonizing on the surface of sponge and filter media that perform biological filtration.

  • Corner filter is dirt cheap
  • Not stir up the water too strong so it’s very useful for small fish tank
  • Good performance of both mechanical and biological filtration
  • Very easy to clean and maintain
  • They are small and cute, small fish and I love them.
  • Not be able to keep the water clear for long
  • The filter media need to be clean frequently
  • Sometimes it floats on the water surface.
Jardin corner filtersJardin corner filters Penn Plax 610 Cascade corner filterPenn Plax 610 Cascade corner filter Jardin corner filtersJardin corner filters

Tip: Sometimes it floats on the water surface because lots of air is accumulated inside of the filter box. If meeting this problem, you can use a suction cup to position the filter in the aquarium wall.

Sponge filters – best for breeding, quarantine or fry tanks

The way a sponge filter works is very similar to the corner filter and it needs an air pump (usually not included in the product) to work. Air tubing is placed in the center of the sponge blowing air out which pulls water through the sponge. Any floating debris in the water will be sucked into the sponge leaving the aquarium with great looking water.



Flowing water and aeration will cause bacteria to build up on the surface of the sponge, don’t worry about this because they are helpful bacteria degrading all the dangerous waste from fish. Water is filtered through a couple of layers of sponge where the mechanical and biological filtration are well performed.

Although the sponge filter is slightly better than a corner filter and just as cheap, it needs frequent cleaning. The advantage is that it does not stir up the water too strong and is ideal for small tanks, fry tanks, and quarantine tanks. Following are sponge filters for different aquarium sizes.

Sponge filter for small 3-5 gallon fish tanksSponge filter for small 3-5 gallon fish tanks Sponge filter for 10 gallon fish tankSponge filter for 10 gallon fish tank Sponge filter for 20 gallon aquariumSponge filter for 20 gallon aquarium Sponge filter for 20-55 gallon tanksSponge filter for 20-55 gallon tanks Sponge filter for large tanks up to 75 gallonsSponge filter for large tanks up to 75 gallons

Read more:

Undergravel filters

Undergravel filters are cheap and simple and were far more common in the early days of popular aquarium keeping. These filters consist of a filter plate which sits under your aquarium gravel, and uplift tubes which move water slowly through your gravel and through the plate. They can be driven by air pumps or air stones for heavier flow.

Penn-Plax Premium Undergravel FilterPenn-Plax Premium Undergravel Filter 40/55 Premium Undergravel Filter 12 by 48-Inch40/55 Premium Undergravel Filter 12 by 48-Inch 70/90 Premium Undrgravel Filter 18 by 48-Inch70/90 Premium Undrgravel Filter 18 by 48-Inch

Undergravel filters may not be the best choice in a tank that’s already established, because you’ll have to tear down your setup to install one. But if you’re just starting out and planning a freshwater or simple saltwater setup, these filters may still be a good choice. Plenty of surface area means good mechanical filtration and excellent biological filtration, using the substrates on your tank’s floor for filter media. (Plus, there are optional chemical cartridges for these filters.)Plants, however, may respond poorly to water flow around their roots.

Undergravel filters require regular gravel vacuuming (which you should do anyway) to avoid having to pull them out once installed. Be aware that these filters can develop stubborn buildup underneath that make them a questionable choice for heavily stocked or reef tanks where tear down is going to be considerably difficult. These filters also lose efficiency over time. Opinions about these filters in the aquarium community are divided.

Read more:

Wet/Dry filters – best for reef or large freshwater tanks

Wet/Dry filters work by trickling water slowly through mechanical media, building up a good amount of oxygen before passing through the biological filter. This factor combined with greater surface area than canisters or power filters mean these filters are the best biological filters you can find and usually offer (or can be modified for) 3 stage filtration.

Best Wet Dry filterBest Wet Dry filter

Wet/dry filtration, especially within sumps (external reservoirs of water plumbed into your tank) is popular and widely used with sensitive systems like large saltwater or reef tanks; as you might expect, then, it’s a bit more complicated than other filters. One benefit of a sump system (there are many!) is that it’s easy to setup natural means of nitrate reduction, like algal filters.

Wet/dry filters can be the complete filtration solution for your aquarium, and there is no better biological filter for heavily stocked systems like reefs, but there are challenges involved that make them less suited to beginners. If you want to learn more about these filters, here’s my short article about it:

Diatom Filters

Diatom filters are specialized mechanical filters that use a filter media called diatomaceous earth; a sediment made of the skeletons of single-celled microbial algae (diatoms), whose unusual pore structure can trap the smallest particles.

Diatom filters are simply the best mechanical filters available. Not only do they provide crystal clear water, they remove algae, parasites, even harmful microbes, keeping your fish healthier, promoting faster healing and greatly improving water conditions.

The drawback with diatom filters is that they become clogged very quickly. Because of this, you shouldn’t use them continuously, so they’re not suitable for primary filtration. However, regular use for short periods is an excellent way to maintain top conditions in your tank, especially if you are having problems with fish health or algae.

Fluidized Bed Filters

Fluidized bed filters house a bacterial bed for biological filtration that won’t have to be disturbed. They suspend fine-grained sand in a column of water – sand has a great surface area but is a bad choice for most biological filters since water flow easily disrupts it. Fluidized bed filters can be a useful supplement for large aquariums with heavy bio-loads.

You’ll also see fluidized bed reactors for chemical media – the same principle suspends fine-grained media for increased surface area and contact time, allowing highly efficient chemical filtration, which is not as effective in higher-flow filters. Fluidized bed devices referred to as filters and not reactors are usually the biological type.

Fluidized bed filters are often advised against because they remove oxygen from your system and quickly build up nitrates in power failures. These filters are best for planted aquariums, where they won’t deplete CO2 and oxygen is less of a concern.

How to choose the best aquarium filter?

How many gallons per hour (flow rate) will I need?

Choose a filter which is rated for your tank size. There is a basic rule that choosing a filter which features a flow rate 4 times larger than the aquarium water volume (gallons). For example, if you have a 10 gallon tank, the filter you will need is one with a flow rate of approximate 40 gph (gallons per hour). It is better to choose a filter with an adjustable flow rate.

Following are links to articles which include the best aquarium filters rated by tank sizes (gallons) for you to easily choose your one.

Which type of filter is best for my aquarium?

Choose a right filter type based on your aquarium size, fish types, requirements, and budget. For normal use on small – medium fish tanks (under 50 gallons), using an external or internal power filter is enough and economic.

For large fish tanks (over 20 gallons) which stock many fish or large-body fish like Goldfish, Koi fish, or cichlids, it is better to use a canister filter to deal with the large amount of waste discharged by them. A canister filter also helps to reduce the maintenance times you have to do each month to keep the tank clean.

For breeding or fry tanks that keep tiny fish, the sponge filter is the best choice if you don’t want the baby fish to be stirred up and killed by a wrong filter.

If you keep Betta fish or other fish that love silent water, you will need a filter which provides a gentle flow rate just enough to keep the tank clean but not stress the fish.

Large capacity: a filter with a large capacity brings a lot of benefits to you. First, it can accommodate more filter media for the most and multi-stage filtration as well as the longer period between maintenance times. Second, with the large filter capacity, you can choose your own filter media and don’t have to use ones same to which are included in the products. That offers the flexibility in using filter media and lowers the maintenance cost of buying the filter cartridge.

Multi-stage filtration: you should choose a filter which can perform multi stages and all types of filtration (mechanical, biological, biochemical). Especially, the biological filtration is the most important stage to keep the aquarium water free of nitrogenous toxins and safe for fish.

Quiet operation: you surely don’t want to place a noisy filter in your home. Read the customer’s reviews to know if a filter is quiet or noisy.

Durability: choose one that can last for a long time without break or leak. Get your attention to the manufacturer’s warranty and the reviews from other customers.

Warranty: Give a consideration to the warranty from the manufacturer.

How to set up/install a fish tank filter?

Position the filter cartridges (if included) in place, layer filter media according to the instruction of the manufacturer. If the manual guide doesn’t mention anything about how to layer the filter media, follow the direction from the intake to output water flow, position the filter media according to this sort: mechanical -> chemical -> biological.

Assemble all essential compartments coming with the product follow the instruction of the user’s manual guide. Some filters like power and canister filters usually come with all you need for the setup; however, some need to buy external equipment to fulfill the installation. They are corner, sponge, and undergravel filers which need an external air pump (buy separately) to operate the entire filtration system.

Position the filter in place. For external canister filter, place it out side the aquarium, under the stand, or inside the cabinet. For external power filter, hang it on one side of the aquarium. For the internal filters (internal power, corner, sponge, undergravel filters), place them inside the aquarium. Remember to place the air pump outside the aquarium and use air tubes to connect it with the filter (which needs to be powered by an air pump).

Plug the filter in and check if it works properly, are there any leaks or breaks? If everything is okay, congratulation! You have succeeded to set up the filter. Remember, the filtration system need a time to be cycled before it can deal well with nitrogenous toxins in the water. If your fish tank setup is brand new, you need to properly cycle the aquarium, this procedure helps to increase the amount of helpful bacteria inside the filter media as well as the aquarium. Remember NOT to add many fish into your new tank until the filter is fully cycled.

How to maintain/clean a fish tank filter?

You should to clean the aquarium filter once a week when changing the aquarium water. For large filter types such as canister filters or wet/dry filters, clean them once a month to keep all things work properly. There are some basic steps for maintaining a filter.

First, plug the filter out, disconnect its housing, open the filtration system and take out of the filter media.

Save the water from the aquarium into a pail for cleaning the filter media. Because chlorine from tap water can kill the helpful denitrifying bacteria living inside the filter media, be sure to rinse them with the old aquarium water which is free of chlorine.

The biological filter media (Ceramide rings, Biomax, Bio-ball…) and pre-filter media can be reuse for a long period; however, the mechanical (foam, floss…) and chemical (activated carbon) ones need sometimes changing. If your aquarium filter uses cartridges specially designed by the manufacturer, check its brand and buy the new ones for changing. You also need to check the manufacturer’s guide to know how and when you should change the filter cartridges.

After rinsing the filter media, reinstall them to the filtration system. Reassemble the filter and plug it on.

Aquarium filter FAQ

How to reduce flow of aquarium filter?

Some fish love to live in a gentle environment, too strong water flow can stress and kill them. If your filter doesn’t feature an adjustable flow rate, there are some other ways to decrease the flow of aquarium filter.

  • Use denser filter media (sponge, floss…) or add more filter media as much as the filter can accommodate to reduce the output flow.
  • Use something (decorations, foams…) to slow the direct water flow from the filter.
  • Use a spray bar to distribute the water through small holes and whereby reduce the flow from the filter.

What is the quietest aquarium filter?

For a power filter, the quietest filter brands are Aquaclear, Aqueon Quietflow. I strongly recommend the Aquaclear filters because its filter capacity is far larger than other power filters rated for the same tank sizes. Besides, the flow rate of the Aquaclear power filters is adjustable to reduce the water flow (as well as the noise produced) but remain the filter efficiency. These filters offer more benefits than any other power filters but cost a very affordable price.

For a internal filter, choose ones which feature an adjustable flow rate and direction which offer the ability to customize to receive your required quietness.

For a canister filter, Eheim Classic series are well-known as the quietest canister filter brand; however, the Fluval 06 series operate so quiet too. And I strongly recommend the Fluval 06 series because it owns much more advanced features than any other canister filter brands.

Should aquarium filter always be on?

Yes, you should leave the aquarium filter on 24/7. As you know, the fish excrete waste into the water during the day, it is a source of nitrogenous toxins (ammonia and nitrite) which need to be processed as soon as possible to not harm the fish. Most helpful denitrifying bacteria live inside the aquarium filter (mostly biological filter media), so the filter should always be on to keep the water constantly circled and filtered.