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Canister Filters for Saltwater

A customer recently asked me a question about using a canister filter on their saltwater aquarium. The customer had read on Reef Central that you should not use a canister filter on a saltwater aquarium, especially on a reef aquarium. That they do not work well, and will cause high nitrates.

This is a topic that you will see differing opinions on. The problem with canister filters is not that they don’t work on saltwater or reef aquariums, they work very well. Any biological filter is going to produce nitrate on a closed aquarium system, it is the natural end product of the nitrogen cycle.

This is why many reef tank owners will remove the bio balls from their wet dry filters, or run their systems on a sump only set up, in an effort to reduce nitrate production. This is why some people are of the opinion that canister filters should not be used on a reef tank. You can get away with this approach if you have a sufficient amount of live rock and substrate in your aquarium to act as your biological filter. In fact, live rock is an excellent source of nitrifying bacteria, and will function as a very efficient biological filter in an aquarium with enough rock. Most reef set ups will work well without a dedicated biological filter, so long as the biological load is not too high, and you are using a good protein skimmer. This method is often referred to as a “Berlin” style aquarium (lots of live rock, good water movement, heavy protein skimming, and no biological filter). Canister filters can still be used on reef tanks, they can be used as additional biological filters in heavily stocked tanks, and can easily be used for whatever chemical filtration media you may want to use.

Saltwater fish only tanks are a different story; in most cases you will need a biological filter to handle the fish waste and biological load, even if your tank has live rock in it. You will also want to have a mechanical filter on a saltwater fish tank, especially if you have large fish in your tank. Most canister filters give you the ability to operate them in different ways. You can use them for biological, mechanical or chemical filtration as needed.

Nitrate is going to be produced in any set up, some more than others. My best advice is to use as much filtration as your aquarium demands. Ammonia and Nitrite should be near zero in an established aquarium, if you are detecting either, chances are your aquariums biological filter is insufficient. Nitrate levels will creep up slowly over time in any system, so whatever filtration method you employ, you still need to monitor your water chemistry. Water changes will remove nitrate from your aquarium, so as long as you are testing your water, and performing regular water changes, nitrates should not be a problem.

Speaking canister filters, here’s a video my staff created to help aquarists set up a canister filter on their aquarium. Canister Filter Video



  1. avatar

    Hi, I totally agree that at present there is to much emphasis upon people being told that they must use this or they must use that.

    With keeping a saltwater aquarium there are so many ways to do things and what works for one aquarists may not work quite as well for another.

    As you say in this great post canister filters are one of these areas. Canister filters if maintained correctly can be an exceptionally powerful form of filtration yet you will need to control nitrates via whatever means. This could be achieved by either an algae bed, deep sand bed, nitrate filter.

    This does not mean that canister filters create excessive nitrates as they don’t. All filters create nitrates – it is the responsibility of the aquarists to manage and maintain the nitrates.

    I have seen some amazing aquariums filtered by canister filters, my fathers is one of them and they should certainly not be discounted on a saltwater aquarium.

  2. avatar

    As a 15+ year marine aquarium hobbiest. I’ve been a reef keeper since “95 and worked in the retail end for 3 years. I am of the school that believes that canister and floss/sponge filters are only as good as they are clean. I mean, They need attention along the lines of a babies diaper needs constant attention. Lots of work!!!
    Secondarily, especially in salt water, much of the interest in the first place is the diversity of life. Any canister/Mechanical filtration is going to literally rob all lower life forms of planktonic foods or suspension foods. Try a sump and excellent 2x sized protien skimmer and watch health and diversity flourish.

  3. avatar

    Hey just found a great video on looking after Marine Fish, Sure you will find it useful as I did 🙂


  4. avatar

    I was wondering if you have to use a wet/dry filter for saltwater aquariums. They are so expensive just wondering if there was another type you could use.

  5. avatar

    You do not have to use Wet/Dry filters on saltwater aquariums, canister or hang on power filters work very well. All these types of filters will provide the necasarry biological, chemical, and mechanical filtration. The main benefits of using a Wet/Dry type filter is the ease of adding a protein skimmer to your system, as well as concealing everything out of sight below the tank. In sump protein skimmers have more choices available, and are more consistant in their performance.


  6. avatar

    can you use sand on bottom for salt water fish ? or not a good thing.

  7. avatar

    You can certainly use sand as a substrate. Just be sure to add plenty of sifters to keep it turned over like gobies, sifterstars, nassarius or other burrowing snails and inverts to keep it turned over and aerated. Alot of fish and inverts need a soft floor to sift through and will love it, but it can be a pain if you have alot of circulation equipment like powerheads or strong returns because it is very light.

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About Dave Acland

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After graduating from Coastal Carolina University with a BS in Marine Science in 1996, I started my professional career in 1997 as an aquarist at Ripley’s Aquarium in Myrtle Beach, SC. This was an amazing experience, in which I gained invaluable hands on training in exhibit design and construction, as well as husbandry skills for a wide range of animals. In 2000 I started working at That Fish Place as one of the staff Marine Biologists, with the responsibility of maintaining one of the largest retail fish holding systems in the world. I presently hold the position of Director of Aquatic Science, where I oversee the operation of our 35,000 gallon retail aquarium systems, and provide technical support for our mail-order and retail store customer service staff. As an aquatic product specialist, I also provide support for our purchasing and marketing departments, as well as contribute web content and analysis. As a Hobbyist I acquired my love of aquariums from my father who was keeping a large aquarium in early 70’s, and set up my first aquarium when I was 12 years old. I have now been keeping aquariums for over 35 years, and through this time have kept more aquariums and types of fish than I can remember. I set up my first Saltwater aquarium in 1992, which led me down the path I still follow today.