Filtration is the literal lifeline of all the inhabitants in the tank. If you have poor filtration, it affects the health and well being of not only the fish and crustaceans but also the plant substrate.
There are a ton of things to look for when buying an aquarium filter (more on that later), but to find the right one, you need to familiarize yourself with the different types of filters there are out there.
The main purpose of aquarium filters is to allow airflow and sufficient oxygen to penetrate your tank, encourage good bacteria growth and it can also remove the floating debris and filter the water. Let’s take a look at the 5 different types of filters.
Table of Contents
- Hanging Filters/Power Filters
- Canister Filters
- Internal Filters/Corner Filters/Box Filters
- Wet/Dry Filters/Trickle Filters
- Undergravel Filters
- Best Aquarium Filter Type Buyer’s Guide
Hanging Filters/Power Filters
Hanging filters are a cheap, simple, and easy way to get filtration for your tank. There are literally thousands of sizes and types that fit almost any aquarium. However, most aquarists today steer clear of them because they’re usually distracting and noisy, and detract from the beauty of a well-built tank.
Hanging filters also reduce the amount of CO2 in your water by agitating the surface, which increases the CO2 release from the water. This is another reason why aquarists with Planted Tanks generally don’t use them—CO2 can be quite expensive when you waste it.
They are easy to set up and are pretty durable compared to other types, and they also deliver superior performance when it comes to the different types of filtration. As suggested by the name, these filters hang easily off the back of the tank and are suitable for many types of fish, giving you versatility.
What also gets people on the hanging filter bandwagon is the fact that these filters are much easier to maintain compared to their counterparts. All it takes is for you to replace the filter cartridges – easy and simple.
How they do it is they remove all the toxins and nitrate from the water that travels through the filter and funnel clean water free of toxins back into your tank so your fish can breathe clean air again.
- Great Entry-Level Choice
- Low maintenance
- Can be very effective
- Doesn’t ever go into the water
- Superior three-stage filtration performance
- Easy to assemble
- Take up less space
- Can be used in both salt and freshwater aquariums
- Most have an adjustable flow rate
Some Good Choices
EHEIM Liberty Filter
- Easy to install, just hang it over the tank edge
- Comes with the filter media
- Longer filter efficiency
- Phenol-free cellular foam cartridge
Why We Like It
The phenol-free cellular foam cartridge will effectively remove pollutants from your tank.
Fluval C2 Power Filter
- Even heat distribution
- Filters 119 gallons of water per hour
- Cleaning indicator
- Clip on and easy to use
Why We Like It
The best part about the Fluval C2 is it alerts you of when the polyfoam needs to be cleaned.
AquaClear 50 Power Filter
- 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 regular products.
Canister filters are without a doubt the best choice for an Aquascape tank. They stay out of sight and are extremely effective at creating crystal-clear water.
Some of the best Aquarists in the world rely on this type of filter for their tanks.
One of the biggest benefits from a canister filter is the potential for customization available for your tank—you can create a custom filter media solution that’s based around what you’re looking for in your filter.
You can modify the amount of flow that’s coming out of the filter, and use attachments to control how that flow acts when it comes out.
Canister filters also have a significantly larger volume than most other filters, which allows for better filtration and beneficial bacteria growth. The simple fact is this: more stuff filtering usually means clearer water.
Canisters are top-rated and the most expensive filters.
They filter using the three phases of filtration and you can add, remove, or change the filtration material. Basically, they are containers that have an in-flow of water and an out-flow of water.
Canisters are great filtering devices since they maintain the cleanliness of the water for a longer time than the other aquarium filters. Also, they are the best option for larger fish tanks because they are powerful filters with vast water flow.
There are canisters available for small, medium, and large fish tanks depending on the amount of water your fish tank holds.
- The choice many professional aquarists use
- Reliable, extremely effective, and only priced in mid-range
- Many models are nearly silent
- Provide the best in filtration performance for all three stages
- Pressurized filtration and traps smaller particles
- Adjustments and customization is available
Some Good Choices
EHEIM Classic 2213 (Check my full review)
- Includes accessories
- Comes with filter media
- Silicon sealing ring
Why We Like It
We like the silicon sealing ring that keeps the pump head safe when closed.
SunSun Multi-Stage Canister Filter
- 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 with manual siphoning.
API Filstar XPS Filter
- Can filter 350 gallons per hour
- Durable and long lasting
Why We Like It
These filters are built to last that can be at your tank’s service for years.
Internal Filters/Corner Filters/Box Filters
Internal filters sit inside the tank and are completely submerged in the water. While these have lost popularity in recent years with the advent of Aquascaping, they still have their uses in filtration.
These filters are usually air-driven with a pump and are meant for small aquariums only, usually no more than 20 gallons. Oddly enough, these are actually one of the most efficient filters, since it’s not taking the water out of the tank to filter it.
They are usually found at the bottom of the tank and their main focus is to prevent debris from filling up and settling inside the aquarium. Let’s say you have a large tank and your main filtration system is the canister filtration but there are dead spots around your aquarium.
Dead spots are areas where the filtration just doesn’t quite reach. A way to solve this issue would be to place internal filters in such areas to guarantee that your tank remains as clean and habitable as possible.
- Some models can be effective in small tanks
- Not meant for aquariums larger than 20 gallons
- Lower price tag
- Can reach areas larger filters cannot
- Can help produce oxygenated bubbles
- Prevents debris from settling and building up
Some Good Choices
EHEIM Aquaball Internal Filter 2210
- Great for 42 gallons
- The direction of the flow is easily controlled
- Flow rate easily set
Why We Like It
This filter has an integrated filter box for the best purification.
Fluval 4 Plus Internal Filter
- Pumps 260 gallons of water every hour
- Clogging indicator
- Adjustable flow rate
Why We Like It
The tank has a clogging indicator that alerts you when the media needs to be swapped out.
Wet/Dry Filters/Trickle Filters
These filters have the maximum amount of beneficial bacteria growth (known as biological filtration). They take advantage of bacteria’s natural cleaning effects by fully exposing them to air, which means the bacteria is at its most effective in cleaning the water of any impure substances.
They do this by exposing as much water 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 as well. They are referred to as wet/dry filters (very literal) due to the exposure to both air and water.
However, they’re not used very often because of their excessive time and maintenance demands. These are so in-depth that sometimes an actual separate tank is used with tons of plant growth and beneficial bacteria.
However intense the maintenance is, it’s worth it—these filters keep the water sparklingly clear. Although it’s also worth it to note that they do clog easily, which makes regular maintenance even more important.
If you’re looking for a wet/dry filter, you’ll have good results with something like this: a 3 Stage Wet/Dry Filter Kit.
- Great for saltwater and freshwater tanks now
- They allow bacteria growth
- Utilizes bacteria’s cleaning abilities to purify water
Some Good Choices
Eshopps AEO13015 Wood 125 No Overflow Filter for Aquarium
- Versatile for any aquarium up to 400 gallons
- Easy to set up
- Dual drain system
Why We Like It
We like how this design is compatible with all tanks and is easy to set up.
These are similar to internal filters in that they’re waning in popularity due to the increase in ‘aquascaped’ tanks. Since they sit under the gravel bed, nobody wants to completely rescape their tank every two months to clean the detritus that’s been trapped under the filter.
These are also not suitable for planted tanks since the plants will likely wrap their roots around the filter great in the substrate. However, it still has its uses in aquariums that aren’t planted. It’s out of the way, and provides ‘invisible’ cleaning throughout the tank.
Note that maintenance is extremely difficult with this type, and sometimes requires a complete rescape to fully clean the filter. 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 quite clean.
Since they are literally called “undergravel filters”, they don’t work quite as well under sand or pebbles. Also, because they clog easily, they need to be used alongside larger bedding.
- Keeps out of the way and remains somewhat invisible
- Cleans gravel beds well
- The large surface area serves to grow nitrifying bacteria well
Some Good Choices
Lee’s 13156 20L/29 Premium Undergravel Filter
- Large plate size
- Stronger UGF plates
Why We Like It
The larger plates will lessen the amount of plates used at once.
Penn Plax Premium Under Gravel Filter System
- Can be invisible
- Easy to set up
- Includes 4 filter plates
- Includes 2 carbon filter cartridges
Why We Like It
The under gravel filter system from Penn Plax comes with 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 an enclosed environment, which is very dense compared to the natural fish habitat. Due to the density and enclosure, the water gets polluted easier, especially if the tank water is not cycled.
When it comes to 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.
To do this, you need to have the best tank filter you can afford. Let’s take a look at what important features to want in a new aquarium filter.
You may have your eye on a filter that you like only to learn later on 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 of tank it’s meant for.
Larger tanks will tend to need more powerful filters, which would also make them larger as well. External filters for larger tanks are the best option because it saves on tank space. You don’t want to crowd your fish in a tank that’s already smaller than their natural environment.
Different types of filters use different technology. There are three parts to the filtration process, and they are geared towards removing solid waste, organic waste and biological waste. We have more on the three-step filtering process later. Let’s just introduce what kind of waste falls into each category.
Biological – Biological waste consists of waste that comes from your fish, their uneaten food and decaying plants.
Organic Waste – Algae and bacteria that develop.
Solid Waste – Similar to biological waste – waste that you can see.
Water Flow – The flow rate of the water in tank filtration systems is measured in gallons per hour. You want a filter that can fill the tank at the ideal speed, not too slow and not too fast because it could affect your fish.
What Type of Filter Do I Need?
Corner filters/Internal Filters/Box filters are extremely common and most beginners use them. They are suitable for small aquariums not more than 15 gallons. They filter the water using an air stone; after a few weeks, colonies of bacteria will develop inside the filter so the water will be biologically clean.
It is not recommended if you want to keep a natural aspect because the position in the corner of the tank will make it very obvious and difficult to hide. They can also be used in addition to larger filters, such as the canister filters.
They are relatively easy to set up, and are pretty quiet plus they are the easiest on your wallet.
Power filters/Hanging filters will strain your water mechanically, biologically, and chemically. These come in different sizes and types and it’s easy to find one that matches your needs. Unlike the previous one, you don’t place the entire filter in the aquarium, only a small tube.
This makes it more appropriate for aquariums with a natural aspect; it’s fairly easy to hide the tube behind decorations or plants. They provide a three-step filtering process and work very well for smaller tanks. Since they never hit the water, they are one of the easiest to maintain and keep clean.
Wet/dry filters/Trickle Filters provide excellent biological filtration, even if they are more expensive. If your tank has a large population, this is the kind of filter you need.
It is composed of two parts and it usually functions based on carbon units, but the newer versions can also contain other filtration materials. As an added bonus, it will also increase the oxygen levels in your tank.
They are much more efficient, which kind of justifies the higher price tag, and they can cut down your tank maintenance. Their slower water flow rate may also be ideal (depending on the type of fish you own).
Undergravel Filters (UGF) – They provide a significant role in reinforcing the good bacteria and chemical reactions that can keep your tank clean. They are very effective, but come with a slew of downsides as well.
They require regular cleaning and have also been identified as the possible culprit to slowing down plant substrate growth. They can also clog easily, which makes your job even harder. One thing you can count on is that they are easier to clean than canister filters.
Canister filters offer mechanical filtration and they are generally used for large tanks. The filter itself is sizeable, but it is placed outside the tank so it will not disturb the visual appearance.
It requires maintenance every few weeks and you have to be sure that every filter is changed in time. It might seem like a lot of trouble, but it’s the only way to be sure that a large tank is cleaned appropriately.
Canister filters are also widely agreed to provide the most beneficial filtration system to your tank. Mechanical, chemical or biological filtering, it has you covered.
Sponge filters allow for aeration but they are not the top performers due to 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. They protect these little critters from being sucked into the filtration system.
They are one of the easiest to use filter systems, so rest assured beginner aquarists, sponge filters are pretty straightforward. They are the most gentle, which also ties into our previous point about using them for newborn fry and shrimp.
With their easy maintenance comes a lower price tag. The sponge also allows good bacteria to make a comfortable home, also contributing to the biological filtration aspect of your system.
Types of Filtration
When it comes to freshwater aquarium filters you should consider a filter that has three stages of filtration: mechanical, chemical, and bacterial.
Good quality filters offer all the stages of filtration that is needed for good water quality and healthy, happy fish.
The mechanical filtration consists of the filter catching waste, debris, or other refuse in the tank. With cleaning, the filter removes all that waste.
Sometimes the waste starts to decompose resulting in chemical changes in the aquarium.
Basically, the mechanical filtration stage removes all the floating debris you can see with your eyes.
Chemical filtration systems work to remove substances such as minerals and metals in our tap water. Doing this can also reduce discoloration, murky waters and also the odor in your aquarium.
The filter keeps the water clean in order to reduce the chemical change of the tank from decomposition. Elements like active carbon that are used in the aquarium filters absorb toxins from the water, making it safe for the fish.
The bacterial/biological filtration is the stage where the water goes into the filter’s elements that are concentrated with beneficial bacteria.
Good places for beneficial bacteria to grow in the filter are the bio-sponges, bio cubes, balls, cartridges, and other materials that are included in the filter or commercially sold.
Common Mistakes with Filters
The most important thing when cleaning the bio part of the filter, for example the bio-sponge, is that you clean it (wash it) in the same water that you extracted from your fish tank.
For example, if you use an aquarium gravel cleaner when you perform a water change, wash the sponge in the bucket with the water that is removed from the tank.
This is very important because the beneficial bacteria on the bio-sponge is thriving; if you wash it in the sink, the chlorine of the tap water will kill the beneficial bacteria in the bio-sponge, rendering the filter useless for bacterial filtration.
It’s like starting over again from scratch, but the fish tank is already populated, so you might place your fish in a dangerous situation.
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.
There are products that contain beneficial bacteria recommended for new aquariums or those not properly cycled.
Your aquarium filter should always be running to make sure the water is always being purified and free of toxins. The filters also provide a slight current, which keeps the fish healthy.
Speaking of the flow rate, looking for a filter that has adjustable water flow settings would be very beneficial. Depending on the type of fish you have, you may need different flow rates so giving yourself that flexibility is crucial.
Also understand that a lot of these filters can be used in tandem with one another to further enhance the living situation of your tank. Where larger canister filters may fail in some dead spots, smaller internal filters will prevail.
How to Install a Filter
The installation process depends a lot on the type of filter you choose, but also on the kind of tank you have. Sometimes you want to conceal the filter so you place it behind large plants, but this can be a problem in the long term. The plant can get caught in the tube and it can destroy the filter or the water stream will be too strong and it will stop the development of the plant.
At the same time, make sure you don’t place the water flow tube directly towards the substrate. This will make the sand spread in the tank and destroy the appearance you worked so hard to build.
Another factor you need to take into consideration is the size of your fish as well as the size of your tank. There is no point in placing a large filter inside a small tank; this will not keep the water clearer and it will not do any good.
It will destroy the plants and the substrate because the water flow will be too strong and it can hurt small fish. If you want to reproduce fish in your tank, make sure nothing disturbs the surface of the water where the fish will place their eggs.
Remember that no filter will last forever, so you need to clean it every once in a while. 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 to you, we’re going to go in deeper and tell you why a filter is vital to the health of your tank inhabitants.
A filter cleans the water, that’s what most people understand. They filter out the unwanted substances that are harmful to your fish and circulates clean water back into the tank. This is all pretty clear and straightforward.
However, what many people don’t realize is that a tank filter wears many hats. Aside from purifying the water, your filter is also responsible for creating water currents (flow rate). They sort of churn the water so that it can be exposed to more oxygen.
More oxygen means a healthier environment for your underwater creatures and the plant substrate to thrive. These two roles explain why smaller fish tanks are easier to maintain.
A filter is also a breeding ground for bacteria – good bacteria. This contributes to the biological filtration part of the filter system. The 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 ad transform them into nitrites then from nitrites to the more harmless nitrates.
It’s amazing what this little device can do for your tank and how the right one can completely transform the living conditions of your tank residents. New improvements are coming out each and every year, so don’t be afraid to play around a little with the newest innovative technology.
Remember that the one you choose needs to be fit for your tank size, and also be relatively easy to clean and maintain. We hope we have imparted valuable knowledge about filter types to contribute to your next decision.
Depending on the type of filter you choose, the frequency of cleaning will differ. They can range from once a week to once every 1-3 months. Make sure you understand how often to clean your new tank filter.
Did You Know
You shouldn’t compromise quality for the price of your filter. Don’t purchase one that’s small because it takes up less space and is more pleasing to the eye. If you have a large fish tank, this will render the small filter useless.