Canister Filter: 15 Things Most Beginner’s Don’t Know

Canister filters are efficient aquarium filters that have a unique purpose which is to push the aquarium water through a filter media and get thoroughly cleaned there. After being cleaned, the water gets pumped back into the aquarium as if it’s brand new.

This kind of filtration system is also popular due to its easy maintenance.

Are Canister Filters Good?

Yes, canister filters are good because they can effectively clean your aquarium water by removing impurities inside the tank, filtering out toxic chemicals in the tank, improving water quality by acidifying it, minimizing noise, and minimizing media cleaning.

It’s no wonder why canister filters are popular because the benefits of using this kind of filtration system speak for themselves.

Other factors add up to the list of benefits canister filters offer compared to other filtration systems . You may refer to the list below:

  • Canister filters don’t take up space inside the tank itself.
  • Canister filter maintenance is fairly easy to do and cleaning it won’t cause stress to the inhabitants of your tank.
  • The large filtration area of a canister filter prevents clogs from happening.
  • Canister filters can be customized according to your aquarium’s needs. You can customize a canister filter’s filter media, water heaters, and diffusers.

What Filter Medias Can I Use For Canister Filter?

Mechanical, biological, and chemical filters are the filter media you can choose from when you get a canister media.

Mechanical filters are a type of filter media that prevents clogs by filtering out larger particles of water that pass through it. With that being said, the mechanical filter must be placed in front of all the other filter media so that debris would get stuck in the first layer of the filter before passing through the others.

There are several types of mechanical filters which include wool, floss, sponges, and bonded pads. The maintenance of mechanical filters would require you to change them often to avoid bacteria build-up.

Biological filters are a type of filter media that houses a great number of beneficial bacteria. A biological filter must be placed right after the mechanical filter so that clogging would be prevented. The build-up of bacteria happening in the biological filter will bring a lot of benefits to your tank such as breaking down toxins that are present in the tank itself.

Ultimately, this would prevent ammonia and nitrate levels from rising too fast. Moreover, there are several types of biological filters, here are the following examples:

  • Sponges
  • Ceramic rings
  • Bio balls
  • Gravel
  • Sand

Lastly, chemical filters are a type of filter media that removes toxins from the water inside a tank and changes the chemistry of the water itself. The chemical filter must always be placed after the biological filter so that it won’t cause a loss of beneficial bacteria in the biological filter.

Chemical filters include the following chemical properties that are in charge of improving an aquarium’s water quality:

  • Activated carbon
  • Ferric hydroxide
  • Resins
  • Zeolite
  • Peat

There’s no best filter among the three types of filter media. The choice is yours to make when choosing the best type of filter media for your tank. All you have to do is know what your aquarium needs and that’s about it.

What Is A Canister Filter?

This is an external canister-type of filter that you can set up outside of your aquarium. A canister filter cleans aquarium water by making use of two tubes; an inlet and an outlet tube.

The former is used for drawing the water into the filter and passes it through the filter media, and then it gets filtered back into the tank via an inbuilt water pump then passes through the outlet tube.

Setting up a canister filter is fairly easy to do since you can adjust the tubes however you like, so long as they stay submerged inside the tank.

Furthermore, this filter is huge, so you’d have to have enough space to accommodate the size of this filter. It’s common for people to set up their canister filters by putting them beside or beneath your tank.

A canister filter can accommodate various filter media such as mechanical, biological, and chemical filters. Also, canister filters are known for their ability to house beneficial bacteria. The more beneficial bacteria growth there is, the more chances there are of having low nitrate levels.

With that being said, the benefits that a canister filter provides, via the filter media it uses, it’s a perfect choice for tanks that are 100 gallons (or more). Canister filters also work wonders with saltwater, freshwater, and planted tanks.

What Is A HOB Filter?

HOB filter is a type of filter that cleans aquarium water by letting it pass through a series of filter media. The HOB filter can use mechanical, biological, and chemical filter media as well.

Hang On Back filters (HOB), also known as Power filters, are a type of filtration system that’s easy to maintain and use, also, these are commonly seen on freshwater tanks.

The question is, can HOB filters be used on saltwater tanks? Absolutely. However, HOB filters can only be used for small to medium-sized saltwater tanks. These filters also make use of chemical filter media most of the time.

Moreover, HOB filters are placed on the tank by hanging them on the back portion of the tank itself. It’s pretty convenient this way because it doesn’t require a lot of space, unlike the canister filter.

Canister Filter V.S. HOB Filter

Now that we’ve defined both filters, which one performs better than the other? You may refer to the table below to see each filter’s pros and cons:

 Canister FilterHOB Filter
PriceMore expensive because it does a better job in cleaning aquarium water. Another thing that makes canister filters expensive is their build. It can accommodate large tanks as opposed to HOB filters.These are more affordable than a canister filter since these are smaller and they can’t filter enough aquarium water.
Space occupiedThis is an external filter, so it doesn’t take up any space inside a tank. However, it will take up some space where the tank is. For instance, a canister filter may not be suitable for a small office.HOB filters are small and don’t take up space inside the tank since they are being  hung from outside the tank (either the back or side of the tank). The only downside of this is you can see the HOB filter through the tank and that will surely ruin the aesthetic of your aquarium.
FunctionCanister filters use mechanical, biological, and chemical filter mediums. This filter utilizes two tubes (an inlet and outlet tube), the inlet tube is in charge of passing the water through the filter media, while the outlet tube gets the filtered water and pushes it back inside the tank. You can add a UV sterilizer and an inline heater to your canister filter. These will ultimately save you some aquarium space since you won’t have to buy a separate heater and UV sterilizer.HOB filters also use mechanical, (minimal) biological, and chemical filter mediums. This filter makes use of an inlet tube wherein water is drawn and passes through the filter media. The clean filtered water is then returned to the tank. Adding a heater to your HOB filter isn’t recommended because this would heat up quickly due to the small size of the filter and may cause melting. On the other hand, there are HOB filters that are being sold that come with a UV sterilizer.  
MaintenanceCanister filters can easily be accessed when it’s time to clean them since they sit right outside the tank. However, when you’re about to clean the filter and change the filter media, that would be a difficult task, especially for beginners. The filter media layers must be properly placed in the correct order to prevent clogging caused by the debris in your tank. Should be cleaned every three to four months.Easier to maintain and clean. Cleaning should be done around once every two weeks. The inlet tubes tend to break easily when cleaning, so be cautious.
Tank size compatibilityLarge and community tanks.Small to medium tanks only. These won’t be able to accommodate large tanks, so you’re better off going for a canister filter instead. 
Effectiveness in housing beneficial bacteriaCanister filters can let beneficial bacteria grow in number in their biological filter medium. The reason behind this is canister filters provide a lot of space in their biological filter media for beneficial bacteria to thrive in.HOB filters can only house a few beneficial bacteria in their biological filter media. The reason behind this is the tank you have is small and there won’t be enough space for the beneficial bacteria to thrive and grow in.
Water flowCanister filters provide controlled water flow for plants and fish inhabitants.Water flow using this filter is limited.

Which One Should You Choose?

The type of filter that you should choose would depend on what type of tank you have. If you have a small to medium-sized tank, then go for a HOB filter. If you have a large or community-sized tank, then you must choose a canister filter.

Of course, other factors would affect your decision when it comes to choosing between these two filters.

  • Your budget. Remember, canister filters are expensive while HOB filters are relatively affordable.
  • Are you a beginner or do you have experience? Canister filters would require a bit of skill from owners since changing the filters can be difficult for beginners. On the other hand, HOB filters are easy to clean and this applies to changing their filter media as well.
  • What species of fish do you own? Every fish’s needs vary when it comes to water flow, some species of fish like slow-paced water flow (fish from ponds and lakes) while some like rapid water flow (rivers, streams, and other bodies of water that have fast currents).

Find out where your fish is classified under and choose the filter that provides the water flow that they’re comfortable with.

Are Canister Filters Loud?

No, canister filters aren’t loud; they’re quiet. The only time canister filters get loud is when it’s under maintenance or if there’s air trapped in the filter itself.

If you want to solve the issue of having air inside your canister filter then all you need to do is gently rock the filter from side to side.

It’s uncommon for canister filters to be loud in the first place. However, there’s a brand of this filter called SunSun which is known to make loud noises. Luckily, there’s a solution for the noise that comes from SunSun canister filters.

  • Check the impeller of your canister filter and check if it’s seated on the hole perfectly. If it’s not secure, it would produce a rattling sound. Ensure that the impeller is inserted properly by tucking it in, afterwards, you should feel a snug fit or a click.
  • Avoid overfilling the canister filter’s basket with filter media as this would cause rattling. Make sure that the baskets don’t wobble when you stack them together, this would indicate that your filter media is not too high.
  • Ensure that the canister filter itself is leveled. If the bottom isn’t leveled, then that would cause vibrations and rattle.
  • Ensure that your canister filter and its hoses are not touching any other object because that will cause vibrations. Vibrations equate to noise.

For more detailed instructions, you may view this video.

Do Canister Filters Leak?

Canister tanks can leak, however, it’s uncommon. If it does leak, there are a few common causes which are a loose hose connection and old o-rings.

There are preventive measures for a canister filter leakage, refer to the bullet point below:

  • Ensure that the hoses are tightly fitted into the canister.
  • Use silicone grease to lube every o-ring in your canister filter. This can be done once or twice a year. However, if you’ve been using your canister filter for years, you have to change the o-ring. This would prevent further damage to the canister filter itself and your home.
  • Lastly, you can check for leaks in your canister filter by placing it inside a plastic container that’s wide enough to hold it. Check the container every once in a while and see if there are any signs of moisture or water build-up.

This video will show you a more in-depth explanation of how to prevent canister filter leaks.

Do Canister Filters Provide Enough Oxygen?

Canister filters do provide enough oxygen, so long as the spray bar that comes with the filter is being used. A spray bar helps with aerating aquarium water, which in turn, increases the oxygen level inside the tank.

A spray bar works by agitating the water inside the tank to increase oxygen levels. The spray bar is usually attached to the outlet of a filter wherein it can evenly spray the entire surface area of the aquarium. Ultimately, that allows oxygen to enter the water inside the tank.

Moreover, if you’re curious to know where you should be putting the spray bar, take a look at your tank because that will help you figure out where you should be putting it. Here’s a guide to help you set up your spray bar:

  • For water flow, place the spray bar at the rear end of the tank.
  • Place the spray bar underwater to have consistent and mellow water flow. Also, by submerging the spray bar underwater, the water splashes won’t create any loud noise as opposed to having it placed above the water.
  • For surface agitation, place the spray bar above the water.

Do Canister Filters Use A Lot Of Electricity?

No, canister filters don’t use a lot of electricity. The majority of canister filters are categorized as low-wattage devices.

Here are a few examples of canister filters and their wattage:

  • Marineland (Magnum 350): 35W
  • Marineland (H.O.T. Magnum) 11W
  • Hagen (Fluval 204): 7W
  • Hagen (Fluval 304): 12W
  • Hagen (Fluval 404): 25W
  • Rena (Filstar XP1): 18W
  • Rena (Filstar XP2): 23W
  • Rena (Filstar XP3): 28W
  • Eheim (2213): 8W
  • Eheim (2215): 15W
  • Eheim (2217): 20W

Do Canister Filters Cause High Nitrate Levels?

Yes, but only if the canister filters aren’t being maintained regularly, cleaned regularly, and if the aquarium water is not being changed regularly.

Canister filters have a high chance of increasing nitrate levels in saltwater tanks compared to freshwater tanks.

To avoid the increase of nitrate levels in freshwater tanks, you must regularly clean your tank. This would include water changes and maintaining the cleanliness of your filter.

So how exactly do nitrate levels build up inside the tank? Nitrate comes from the leftover detritus (decomposing organic matter) and debris that’s caught in the filter media. As this continuously decomposes, if you don’t clean your filter, it will result in the growth of nitrates.

How To Prevent My Canister Filter From Becoming A Nitrate Factory?

Clean your canister filter monthly to prevent nitrate levels from rising and regularly check your aquarium’s nitrate level and ensure it stays below 5 ppm.

Avoid letting nitrate levels go beyond 5 ppm because this will be bad for the inhabitants in your tank due to excess algae growth. A small amount of algae is normal in any tank, however, too much of this would be dangerous for your fish.

Do Canister Filters Aerate Water?

No, canister filters don’t aerate water since they don’t use an air pump. It’s not necessary for canister filters to use an air pump since they provide enough surface agitation to the aquarium water.

The surface agitation that comes from external filters, like a canister or box filter, would suffice in providing oxygen for your fish, so there’s no need to purchase a separate air pump to provide aeration.

You might be wondering if there’s a difference between aeration and oxygenation, well, there is. The difference between the two is the process in which they provide oxygen to the inhabitants in the tank.

Oxygenation provides oxygen by using an oxygen generator. This dispenses diffused oxygen into the tank. This is used when the oxygen levels in a tank drops to a dangerous level.

Aeration on the other hand provides oxygen by using an air compressor (air pump). This spreads diffused oxygen to the floor of the tank. Moreover, aeration maintains the temperature of the tank as well as prevents the growth of toxic algae.

An air pump’s purpose is to provide enough concentrated oxygen and to force water through a filter. Air pumps are also the ones responsible for creating those tiny bubbles you see in aquariums.

How Long Do Canister Filters Last?

Canister filters would last at least five years. It’s also possible for canister filters to last more than five years, provided that the crucial parts of the filter are replaced when it shows signs of wear (e.g. o-rings).

The reason why people prefer canister filters over other types of filter is because of its durability. Canister filters are usually manufactured by Germany and Italy and both countries are known for providing durable and long lasting equipment for aquarium needs.

Moreover, most, if not all, canister filters offer long warranties. So you shouldn’t worry if you experience some troubles with your unit since it will be covered by its warranty. On a side note, it’s rare for people to experience any sort of trouble with their canister filter in the first place.

Fluval FX6, Fluval 207, and SunSun HW-302 are the most popular and high-rated canister filters in the market.

Both the Fluval and SunSun brands have been in the aquarist field for a long time and these have also become quite popular over time as well. The canister filters aforementioned are high-quality and durable filters that will provide performance that’s close to perfect.

It didn’t hit the perfect mark in terms of what it provides because each canister filter has its own set of cons. For instance, the Fluval 207 doesn’t come with a spray bar, the Fluval FX6 is too expensive, and the SunSun HW-302 has a few plastic parts that tend to be flimsy.

Check them out here:

Fluval FX6

Fluval 207

SunSun HW-302


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