The 5 Filter Types and Their Uses in Planted Tanks

Filtration is the lifeline for your tank occupants, and all creatures and plants need clean water to survive.

There are many things to consider when buying an aquarium filter. To find the right one, you should familiarize yourself with the five different (and popular)  filter types.

An aquarium filter’s job is to allow airflow and sufficient oxygenation of your tank water, which encourages good bacteria growth. It removes floating debris and filters the water. Here are the five different aquarium filter types.

Top 5 Filter Types

1. Hanging Filters/Power Filters

Hanging filters are a cheap, simple, and easy way to get filtration for your tank. Thousands of hanging filter sizes and types are available and fit almost any aquarium. However, most aquarists avoid them because they’re usually distracting and noisy and detract from the beauty of a well-built tank.

By agitating the water surface, hanging filters reduce the amount of CO2 in your water, which increases the CO2 release from the water. This is another reason aquarists with planted tanks generally don’t use them—CO2 can be pretty expensive, so why waste it?

These filters are easy to set up and are more durable than other filter types. They also deliver superior performance regarding the different types of filtration. As suggested by the name, these versatile filters conveniently hang off the back of the tank and are suitable for many types of fish.

What also gets people on the hanging filter bandwagon is that these filters are much easier to maintain than their counterparts. All it takes is for you to replace the filter cartridges – easy and simple.

Hanging filters remove most toxins and nitrates from the water that travels through the filter before funneling clean water free of toxins back into your tank so your fish can breathe clean air again.

Pros of Hanging Filters

• Great entry-level choice
• Low maintenance
• It can be very effective
• There is no need to place it in water, which saves space
• Superior three-stage filtration performance (some have more)
• Easy to assemble
• It can be used in both salt and freshwater aquariums
• Most have an adjustable flow rate

Some Good Hanging Filter Choices

Fluval C2 Power Filter

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• Provides even distribution of good bacteria to help the nitrifying process
• Filters 119 gallons of water per hour
• Cleaning indicator (when to replace the filter cartridge)
• Clip-on and easy to use

Why We Like It

The best part about the Fluval C2 is that it alerts you when the polyfoam needs cleaning.

AquaClear 50 Power Filter

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• Energy efficient
• Easy installation
• 2 year warranty
• Larger filtration volume

Why We Like It

We like the larger filtration volume (up to 7 times larger) than other filters.

2. Canister Filters

Canister filters are, without a doubt, the best choice for an Aquascape tank. Canister filters stay out of sight and are highly effective at creating crystal-clear water.

Most of the best aquarists and full-size aquariums rely on this type of filter for their tanks.

One of the most significant benefits of a canister filter is the customization potential, offering your tank the best service. Create a custom filter media solution based on what you’re looking for in your filter.

You can modify the amount of flow from the filter and use attachments to control how that flow distributes when it leaves the outlet valve.

Canister filters also have a significantly larger filtration chamber for large-volume filtration than most other filters, which allows for better filtration and beneficial bacteria growth. Simply put, when you have loads of filtration media working to clean your tank water, it means clearer water.

Canisters are top-rated and the most expensive filters.

These filters clean water using the three phases of filtration. You can add, remove, or change the filtration material. The filter housing has an in-flow of water and an out-flow of water.

Canisters are great filtering devices since they maintain the water’s overall cleanliness, ensuring the water stays cleaner than other aquarium filters. Also, they are the best option for larger fish tanks because they are powerful filters with vast water flow.

Canister filters are available for small, medium, and large fish tanks, depending on how much water your tank holds.

Pros of Canister Filters

• The choice many professional aquarists use
• Reliable, extremely effective, and priced from mid to high- range
• Most models are nearly silent
• Provide the best results in filtration performance for all three stages
• Pressurized filtration that traps smaller particles
• Adjustments and customization are available

Some Good Choices

1. EHEIM Classic 2213 (Check my full review)

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• Includes accessories
• Comes with filter media
• Silicon sealing ring

Why We Like It

We like the silicon seal ring that keeps the pump head safe when closed and in operation.

2. SunSun Multi-Stage Canister Filter

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• Good with high water pressure
• 3 media trays
• Self-priming pump
• Quiet filtration

Why We Like It

We like the self-priming pump that saves you time wasted on manual siphoning.

3. Internal Filters/Corner Filters/Box Filters

Internal filters sit inside the tank and are usually fully submerged in the water. While these have lost popularity in recent years with the advent of Aquascaping, they still have their filtration uses, even if they are a little clunky.

These filters are usually air-driven with a pump and are meant for small aquariums, usually no more than 20 gallons. Corner filters are some of the most efficient filters since filtration doesn’t take water out of the tank to filter it. You’ll usually find these filters sitting at the bottom of the tank, and their primary purpose is to prevent debris levels from rising and forming a layer inside the aquarium. 

Perhaps you have a large tank, and your primary filtration system is a canister filter, but there are dead spots around your aquarium. Dead spots are areas where the filtration doesn’t quite reach. Solve this issue by placing internal filters in the dead spot areas (usually corners) to guarantee that your tank remains as clean and habitable as possible.

Pros of Corner Filters

• Some models can be effective in small tanks
• Ideal for aquariums smaller than 20 gallons
• Lower price tag
• Can reach and clean areas that external filters cannot
• It can help oxygenate the water with air bubbles
• Prevents debris from settling and building up

Some Good Choices

1. Hygger Aquarium Corner Filter 135 GPH for 5~15 Gallon Fish Tank

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• Three-way filtration, including biological, mechanical, and chemical filtration
• 135 GPH flow rate 
• Ideal for 5-15-gallon tanks
• Two types of water outlets for different flow effects 
• Four suction cups for attachment on either side of the corner filter

Why We Like It

The filter is quiet and effective and can be neatly hidden in a corner by a tall plant. The two flow rate settings offer some selection opportunities to fit your tank.

2. Aquapapa Corner Filter

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• Multiple filter material layers 
• See-through filter casing to check filter status
• Aerator connection 
• Mechanical, biological, and chemical filtration 
• Needs an additional air pump

Why We Like It

Due to the clear plastic housing, the filter blends into the tank much better for aesthetic appeal. The filter cleans dead spots in the tank. 

We think you may be interested in: Best Pond Pump

4. Wet-Dry Filters or Trickle Filters

These filters create the maximum amount of beneficial bacterial growth, which cleans a tank through biological filtration. The trickle filter takes advantage of bacteria’s natural cleaning effects by fully exposing the correct bacteria-forming filter materials (such as ceramic beads) to air, which means the bacteria is most effective in cleaning the water of any impure substances.

They do this by exposing as much water surface to air as possible. The water slowly trickles (hence the name) over a container that holds plastic balls or plastic strands. They work well with saltwater tanks but have since been proven beneficial for freshwater tanks. They are called wet-dry filters (very literal) due to their exposure to air and water.

However, they’re rarely used because of their slow filtration time and intense maintenance demands. The trickle unit can be so large that a separate tank is used with tons of plant growth, exposed surfaces, and beneficial bacteria for large tanks.

Despite the intense maintenance, it’s worth it—these filters keep the water sparkling clear. However, it’s also worth noting that trickle filters clog easily, making regular maintenance even more important.

If you’re looking for a wet-dry filter, a few good units are on the market to help you start your trickle filtration system.

Pros of Wet-Dry Trickle Filtration

• Great for saltwater and freshwater tanks 
• Exposed filtration surfaces allow bacterial growth
• Utilizes bacteria’s cleaning abilities to purify water

Some Good Choices

1. Bluecoco Premium Multi-Layer Aquarium Filter

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• Filtration rack that mounts on the side of the tank
• Separate units for different filter materials
• Air exposure to water when it trickles over filter materials
• Aerates water with a waterfall feature

Why We Like It

The integrated filter process and elegant construction are visually pleasing, and you’ll enjoy watching the water trickle back into the tank. Many different filtration materials, including planted sections, can be used to filter the water.

2. Doonarces 5 Grids Acrylic Fish Tank Filter Box

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• Side-mounted filtration unit that has five chambers for different filtration media
• Water trickles across the container terraces, exposing it to air
• Waterfall return section 
• Intake tap on the highest filtration chamber

Why We Like It

The filter boxes are shallow enough to create a cascade effect of the water across different filtration media, introducing oxygen to the water. It’s practical and customizable.

5. Undergravel Filters (UG Filters)

Like internal filters, these undergravel filters are less popular due to the increase in ‘aquascaped’ tanks where people like to have an external (hidden) filter. As you place undergravel filters under the gravel bed, nobody wants to completely re-scape their tank every two months to clean the detritus trapped under the filter.

These filters are also unsuitable for heavily planted tanks since the plants will likely wrap their roots around the filter grate below the substrate. However, UG filters still have their uses in unplanted aquariums. UG filters are out of the way and provide “invisible” cleaning throughout the tank, reducing the need for manual siphon cleaning.

The biggest downfall is that maintenance is challenging with this filter type and sometimes requires a complete re-scape to clean the filter fully. All this sounds exceptionally hard to maintain, and it could turn you off this product for good, but there is a silver lining. Undergravel filters keep your aquarium beds relatively clean.

Since they are called “undergravel filters,” they don’t work quite as well under sand or pebbles. Also, because they clog easily, they need to be used with larger-size particle substrates.

Pros of Undergravel Filters

• It uses very little space in the tank and remains somewhat invisible
• Cleans gravel beds well
• The large surface area serves to grow nitrifying bacteria for nitrogen processing

Some Good Undergravel Filter Choices

1. CORISRX BEST OF YOUR LIFESTYLE Undergravel Filter

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• Large plate size
• Height adjustable lift tube 
• Perfect for saltwater or freshwater tanks
• Cleans gravel by filtering through the plate with nitrifying bacteria

Why We Like It

The white color of the plate is more visually pleasing, with pale or white substrates. Comes with two connectable plates, and more can be added (but purchased separately) for larger tanks. 

2. Penn Plax Premium Under Gravel Filter System

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• Can be invisible
• Easy to set up
• Includes four filter plates
• Includes two carbon filter cartridges

Why We Like It

The undergravel filter system from Penn Plax has everything you need to remove odors and water discoloration while maintaining water quality.

Best Aquarium Filter Type Buyer’s Guide

A freshwater aquarium filter is a necessity for any fish tank. The aquarium is a very densely planted enclosed environment compared to the natural fish habitat. Due to the density and because it’s an isolated system where water doesn’t dilute with fresh water coming in, the water gets polluted more easily, especially if the tank water has poor circulation through a filter.

Regarding fish tanks, the goal is to recreate the natural habitat in a relatively small and enclosed tank with a high density of plants, fish, and other water inhabitants like snails, shrimps, and more.

You must use the best tank filter for your aquarium’s needs to do this. Let’s look at what essential features your new aquarium filter must have.

Tank Size

You may have your eye on a filter that you like, only to discover that it’s not the right fit for your tank size. Fortunately, some types of filters work well with a wide range of tank sizes and water types. Before you press “order,” make sure you read the description clearly because manufacturers will clearly state the type and size of the intended tank.

Larger tanks will need more powerful filters, making them larger as well. External filters for larger tanks are the best option because they save on tank space. You don’t want to crowd your fish in a tank with chunky filters that further shrink their available space.

Filtration Type

Different types of filters use other technologies. There are three parts to the filtration process, all geared toward removing solid, organic, and biological waste (there’s more on the three-step filtering process later). Here’s how to classify the waste produced in your tank:

Biological Waste – These organic wastes consist of feces, skin cells, and dead fish that may accumulate in your tank. Uneaten food, decaying plants, algae, and harmful bacteria also make up biological waste.

Solid Waste – The wastes you can see, with particles visible to the naked eye.

Chemical Waste – The build-up of gasses, chemicals, and other materials that are dissolved into the water, harming the tank occupants.

Water Flow

The water flow rate in tank filtration systems is measured in gallons per hour (GPH). You want a filter that can circulate the tank volume at enough speed to cycle through it several times in an hour. However, filters with too strong motors will scare fish, so find a balance.

Motor

The filter motor must be powerful enough to provide an adequate water flow rate to circulate the tank’s volume. Still, it also needs to feature electrically safe components and easy access for cleaning, and it should operate quiet enough that it doesn’t create annoying background noise.

Impeller

The size of the impeller is essential as it needs to be big enough to force water into the motor. The impeller axle should be made of a durable material that won’t quickly wear and seize up. Impellers are often the first part of the motor that becomes damaged due to regular use.  

Media Basket Size

The size of the media baskets determines how much filtration media you can use, which is how your tank’s water gets cleaned. Larger baskets mean more filter material and more cleaning. Filters may also have extra media baskets that you can fill with specialized filter materials.

What Type of Filter Do I Need?

Corner Filters, Internal Filters, or Box Filters 

These filters are widespread, and most beginners use them. They are suitable for small aquariums of 15 gallons or less. These filters circulate and clean the water using an air stone; after a few weeks, colonies of bacteria will develop inside the filter, cleaning the water biologically.

If you want to keep a natural appearance in your tank, the filter’s position in the corner of the tank will make it very obvious and difficult to hide. Use corner filters in addition to larger filters, such as the canister filters.

Corner filters are relatively easy to set up, pretty quiet, and the easiest on your wallet.

Power Filters or Hanging Filters 

These filters will strain your water in three stages: mechanically, biologically, and chemically. Filter units come in different sizes and types, and finding one that matches your needs is easy. Unlike the previous filter type, you don’t place the entire filter in the aquarium. Only a small tube connects to the filter inlet.

Unlike other filters, hanging filters are aesthetically more appropriate for aquariums with a natural appearance. It’s relatively easy to hide the tube behind decorations or plants. Since the filters are never submerged in water, they are easy to maintain and clean.

Wet-Dry Filters or Trickle Filters 

These filters provide excellent biological filtration, even if they are more expensive. This is the filter you need if your tank is large with a diverse population.

It comprises two parts and usually functions with carbon units, but the newer versions can also contain other filtration materials. As a bonus, it will also increase the oxygen levels in your tank.

As these filters are much more efficient, they justify the higher price tag and can reduce tank maintenance expenses. Their slower water flow rate may also be ideal (depending on the type of fish you own).

Undergravel Filters (UGF)

UGFs play a significant role in reinforcing the good bacteria and allowing the chemical reactions that can keep your tank clean. These are very effective filters, but they also come with a slew of downsides.

Regular cleaning is one challenge that has proven to slow down plant growth due to substrate disruptions. UGFs can also clog easily, which makes your job even harder. One thing you can count on is that they are fairly simple to clean once you’ve removed them from the tank.

Canister Filters 

These filters offer mechanical filtration (though some also have biological and chemical filtration chambers) and generally suit large tanks. The filter itself is sizable but placed outside the tank, so it will not disturb the visual appearance—just hide it in a cupboard.

Canister filters require maintenance every few weeks, and it’s essential to check the filter is changed routinely. It might seem like a lot of trouble, but it’s the only way to ensure an appropriately clean large tank.

Experts agree canister filters provide the most beneficial filtration system for your tank. Mechanical, chemical, or biological filtering will keep your tank covered.

Sponge Filters 

While sponge filters allow for aeration, they are not the top performers due to their slow water flow. These work well if you have smaller creatures in your tank, such as the Red Cherry Shrimp, or during breeding season when your fish spawn eggs or fries hatch. Sponge filters protect these little critters from being sucked into the filtration system.

Sponge filters provide the easiest-to-use filter system, making them ideal for beginner aquarists since they are also pretty straightforward. You can expect a gentle aeration and slow filtration process.

With their easy maintenance (just remove the sponge and rinse) comes a lower price tag. The sponge also allows good bacteria to make a comfortable home, contributing to the biological filtration aspect of your system.

Types of Filtration

When it comes to freshwater aquarium filters, you should consider a filter with three filtration stages: mechanical, chemical, and bacterial.

Good quality filters offer all the filtration stages needed for good water quality and healthy, happy fish.

Mechanical Filtration

Mechanical filtration involves the filter catching waste, debris, or other refuse from the tank water. The filter removes all that waste by circulating the water through the filtration media.

Sometimes, the waste decomposes in your tank, resulting in chemical changes, so removing waste before it decays is essential. The mechanical filtration stage removes all the floating debris trapped in the filter.

Chemical Filtration

Chemical filtration systems work to remove substances such as minerals and metals in our tap water. Doing this can also reduce your aquarium’s discoloration, murky water, and nasty odors.

The filter keeps the water clean by reducing the chemical changes in the tank caused by decomposition. Elements like activated carbon in the aquarium filters absorb toxins from the water, making it safe for the fish.

Biological Filtration

Bacterial or biological filtration is when the water goes into the filter’s elements and interacts with concentrated beneficial bacteria. The bacteria turn certain substances into useful byproducts, such as converting ammonia into valuable nitrates.

The bio-sponges, bio cubes, balls, cartridges, and other materials included in the filter or commercially sold are good places for beneficial bacteria to grow in the filter.

Common Mistakes with Filters

The most important thing when cleaning the bio part of the filter, for example, is cleaning the bio sponge (wash it) in the same water you extracted from your fish tank.

For example, if you use an aquarium gravel cleaner or siphon during a water change, wash the filter sponge in the bucket of water from the tank.

This step is crucial because the beneficial bacteria on the bio-sponge are living organisms; if you wash it in the sink, the tap water’s chlorine will kill the bacteria colonies in the bio-sponge, rendering the filter useless for bacterial filtration.

It’s like starting over from scratch, but since the fish tank is already populated, you might endanger your fish if the filter has a “new” sponge. New sponges need to be washed in water from the tank before installation, so beneficial bacteria can start to colonize it before you put it in the tank.

Also, when filling your tank with tap water (before adding the fish), treat the water with products that remove chlorine, making the water safe for the fish.

Some products contain beneficial bacteria recommended for new aquariums or those not properly cycled.

Your aquarium filter should run at all times to ensure the water is constantly circulating, filtered, and toxins-free. The filtration also provides a slight current, which keeps the fish healthy.

A filter that has adjustable water flow settings is very beneficial. Depending on your fish type, you may need different flow rates, so having that option is crucial.

Also, understand that many of these filters can work in tandem with one another to enhance the water conditions of your tank further. Smaller internal filters will prevail, whereas larger canister filters may fail in some dead spots.

How to Install a Filter

The installation process is determined by the type of filter you choose and the kind of tank you have. You probably want to conceal the filter, and you can place it behind large plants, but this could become a problem in the long term. The plant can get caught in the water intake, which can destroy the filter, or the water suction will be too strong and stunt the plant’s development.

However, do not direct the water outlet tube directly towards the substrate. This will spread the sand in the tank and destroy the appearance you worked so hard to build.

Another important consideration is the size of your fish as well as the size of your tank. There is no point in using a large filter inside a small tank; this will not keep the water clearer and will likely kill your fish.

Oversized filters will destroy the plants and the substrate because the water flow is too strong, and it can hurt small fish. If you want to breed fish in your tank, ensure nothing disturbs the water surface as many fish’s spawned eggs collect there.

Remember that no filter material lasts forever, so you need to clean it occasionally. In this way, you will maintain a perfect habitat in your tank.

Is a Filter Necessary?

Now that you know more about the different types of filters available, we’ll address the intensely debated question of whether a filter is necessary for all tanks. The short answer: Yes, a filter is vital for the health of your tank inhabitants, no matter the size of the tank. 

A filter cleans the water, as we all know. Filters remove the unwanted and harmful substances that can poison your fish and circulate clean water back into the tank. 

Many people don’t realize that a tank filter also has other functions. Aside from purifying the water, your filter also creates water currents (determined by the flow rate). They churn the water, exposing it to more oxygen stimulating fish to swim.

More oxygen means a healthier environment for your underwater creatures and the plant substrate. It’s easier to achieve oxygenated, clean, and moving water in smaller fish tanks as there’s less water volume to move. 

A filter is also a breeding ground for bacteria – good bacteria. This contributes to the biological filtration part of the filter system. Good bacteria break down harmful molecules into safer ones. For example, ammonia can be detrimental to your fish, and the bacteria can break them down and transform them into nitrites and more harmless nitrates, which your plants love.

Conclusion

What this little device can do for your tank and how the right filter can completely transform your tank environment is fantastic. New filter designs and innovations are constantly hitting the market, so don’t be afraid to play around a little with the latest filter technologies.

Remember that the aquarium filter you choose needs to be appropriate for your tank size and relatively easy to clean and maintain. Time to go filter shopping!

Expert Tip

Your cleaning routine will depend on the type of filter you choose. Cleaning schedules may be as often as once a week to once every 1-3 months. Ensure you understand how often to clean your new tank filter.

Did You Know?

You shouldn’t compromise quality to get a cheap filter. Don’t purchase a too-small filter simply because it takes up less space, is more affordable, and more pleasing to the eye. If you have a large fish tank, you need the right size filter or a series of filters.