Canister Filters On Saltwater Aquariums: How To Use Them

The Go-To filter in the world of freshwater aquariums, but there is an ongoing debate in the saltwater hobby:

Canister Aquarium Filters are a stand-alone filter that houses various filter media outside of the aquarium. Water is pumped from the tank, through the filter, and back to the aquarium. Regular cleaning is required to prevent a build-up of waste material causing high nitrates and phosphates.

So the short answer is Yes, but there are better alternatives available. The main reason why people use a canister filter on their new saltwater aquarium could be for the following reasons:-

  • They had one from their previous freshwater setup
  • They are a cheaper filter to buy
  • Many first saltwater tanks are not drilled for a drain to a sump
  • They are usually stocked at many local fish stores and can be easily pushed onto an unsuspecting buyer.

What Saltwater Media Can You Use In A Canister Filter?

Careful selection of media and the order in which it is stacked in the canister will allow you to successfully run a canister filter on smaller aquariums.

The two main problems with the canister filter are that you are usually unable to clearly see what is going on in the filter, and their size limits the amount of filter media you can place in each canister.

To successfully filter a saltwater aquarium you need 3 types of filtration in your system:-

  1. Mechanical Filtration
  2. Biological Filtration
  3. Chemical Filtration

To find out lots more information on each of these types of filtration, I have a great article all about it called ‘Types of Aquarium Filter Media & What They Do‘. Click HERE to read it.

The main types of filtration you can easily accomplish with a canister filter on a saltwater aquarium is Mechanical Filtration & Chemical filtration.

The Live Rock/Dry Rock you have in your aquarium will eventually take care of the Biological Filtration as your aquarium cycles and matures.

Aquarium Mechanical Filtration In A Canister Filter

Sponges and filter floss are the best way to accomplish the mechanical removal of solid matter from your water. Most canisters come with purposely shaped pads to perfectly fit inside. You can also purchase more as they wear out.

Canister Filter Sponges
Typical Canister Filter Sponges

Filter floss in a chamber is a cheaper way to filter out the solids. You can just remove it and replace with new floss each week.

Aquarium Chemical Filtration In A Canister Filter

This is where you can really improve the efficiency of a canister filter with ease because of some great products that are available.

Most seasoned canister users will place the following two products into the two chambers following the filter floss:

1. Purigen


This is a synthetic filter media that is designed to absorb Ammonia, Nitrite and Nitrate compounds. It also has an added benefit of polishing the water, similar to what Activated Carbon does.
As the Purigen becomes exhausted it changes its color to dark blue and eventually black. The great benefit to this product is that you can recharge the media by removing it and washing it in a bleach and water solution.

The recommended usage is 1ml for every gallon

>>Find it HERE at<<

2. Chemi-Pure

Chemi-Pure Elite

This is a manufactured mix of Activated Carbon and a ‘Purigen’ type of ion-removing compound that helps to remove organic waste and absorb the harmful Ammonia, Nitrate and Nitrate compounds. It comes in a bag which can be placed in a tray and will have to be disposed of once it is exhausted.

The manufacturer recommends you change this out every 4-6 months providing you have sized the amount of Chemi-Pure correctly. Once your aquarium begins to get cloudy, it’s time to change the media.

You can now also get Chemi-Pure Elite which adds a Ferric Oxide material to the media to help reduce Phosphates and Silicates at the same time, but only lasts 4 months.

The recommended usage is 1 unit for every 5 – 40 gallons

>>Find It HERE at<<

If You Have A Forth Media Tray Left…

I highly recommend you add in a little media to greatly help with Biological Filtration. I mentioned that your rock will be your main biological filter, but if you have space left in your canister then I highly recommend MarinePure Biofilter Spheres!

MarinePure is a relatively new form of biological filter media. They are available in ‘Blocks, Plates, and Spheres’. These are being installed in many aquarium sumps and canister filters to provide more surface area for bacteria to colonize.

The benefit of these new products is that they are extremely porous and hardly trap detritus!

MarinePure is the most popular product available and you can click the link to see them at
I recommend the spheres as they are simple to fit into any canister tray size. The blocks and plates will be too big and you will have to ‘Saw’ them to fit, thus wasting money.

>>Find the MarinePure products Here at<<

How Often Do You Need To Clean An Aquarium Canister Filter?

My recommendation is WEEKLY. This is the biggest reason why canister filters cause their owners trouble. A canister filter left to accumulate detritus and waste will soon reduce its flow and allow the dirt to begin to break down and increase Nitrates.

You have probably heard of canister filters becoming ‘Nitrate Traps’ on many forums, this is why.

The second reason to keep them clean is that as the filter becomes clogged, the flow rate though it will decrease and less water will pass through the media to be filtered.

Like any piece of equipment on your aquarium, keeping it regularly cleaned, maintained and the media replaced will see many years of successful use.

Can I Use A Canister Filter For A Fish-Only Saltwater Aquarium?

Yes. They usually work well on Fish-Only aquariums to help remove detritus via mechanical filtration. Corals require higher quality water than a fish-only aquarium, so this is a good way to start and get your maintenance routine figured out before you want to progress onto corals.

Most Fish-Only canister filters use lots of filter floss and Purigen or Activated Carbon to help remove soluble fish waste and polish the water.

Canister Filter Pro’s & Con’s On Saltwater Aquariums

Every piece of equipment you intend to use on your aquarium should have some thought into how it will work on your setup. Everyone has a different setup and while one item may not work for them, it could work perfectly for you.

Canister Filter Pro’s

  • Relatively inexpensive
  • Many aquarium owners may already own one
  • Easy to maintain
  • Spare parts are easily accessible
  • Does not require a drilled aquarium
  • Multiple trays to allow various filter media types

Canister Filter Con’s

  • Need regular maintenance
  • Limited to the amount of media in each basket
  • Unable to place additional equipment inside it
  • As they clog all the filter media becomes effected
  • Have to open and inspect the canister to check media usage
  • Only really useful for smaller aquariums under 75 gallons

Which Canister Filter Do I Recommend For Saltwater Aquariums?

I have worked on many successful aquariums that use canister filters and by far the most popular and easy to work on are the ‘Eheim Classic’ Range of canisters. They have been around for decades and you may already own one!

In my eyes, if this was the route I was to take, then I would be buying an Eheim!

>>You can see more information, read the great reviews and find the latest prices on the large range of the most popular Cansiter Filters HERE at<<

Other Alternatives

A Sump! There are many reasons why most saltwater aquariums utilize a sump and the benefits are worth the extra cost it takes to have one on your system. If this is your first saltwater aquarium then I can tell you now that it won’t be long before you are planning your next tank!

Use this tank to learn and then make the jump to a drilled aquarium and sump for your next.

If nothing else, a sump allows you to hide all the equipment so all you see is the raw beauty of the fish and corals without the distraction of pipes, cables, and equipment all over the place!

If you would like more information on how sumps work and what you need, you can find all the information in my article:

Aquarium Sumps: This Is Everything You Need To Know!

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Hi, I'm Richard and I have been an avid aquarist for over 30 years with a passion for Saltwater Aquariums. I love to pass on my knowledge to help others get the same amount a pleasure out of this hobby as I do. View my About Me page to find out more about me & my mixed reef aquarium.

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