Nitrate, and Ways to Control It in Saltwater Aquariums

Fish tank
Moto "Club4AG" Miwa/Flickr/CC By 2.0
  • 01 of 07

    What Are Nitrates and Where Do They Come From?

    What Is Nitrate?

    Nitrate is the waste by-product of nitrifying bacteria (nitrobacters), which develops in the final phase of the nitrogen cycling process. It is what makes an aquarium's biological filtration system function and stay in balance.

    Why Is Nitrate a Problem Element?

    When nitrate is allowed to accumulate or build-up to high levels it can effect the health of the animals you are keeping, and because marine plants and algae feed on nitrate, this is one of the main reasons problems with...MORE algae blooms occur.

    What Is an Acceptable Level?

    By many accounts, the optimal amount of nitrate in any type of saltwater system is an immeasurable one, but an acceptable range for fish-only tanks is from 10 to 40 ppm. Although fish-only tanks may run at much higher levels, sometimes with no ill effects, this is not recommended. In reef systems, even a minor level of nitrate can cause damage as well as death to delicate corals, anemones and other invertebrates, as well as some crustaceans. The acceptable range of nitrate for reef tanks is 0.25 ppm, but not more than 5 ppm.

    Other Sources of Nitrate

    Even though nitrate is a natural element in aquariums, when doing water changes and topping-off the tank to replace water lost from evaporation, if using unpurified tap water, and/or a brand of sea salt mix that may contain a high level of this element in it, instead of reducing the nitrate, you can just be putting it right back into the aquarium. Therefore, it is wise to filter tap water before using it, and choose what sea salt you are going to use carefully.


    • Controlling Nitrates With Mangrove Plants
    • Natural Nitrate Reduction (NNR) Filtration
    • Using Denitrator Units, Absorption Compounds and Additives
    • Multiple Water Change Reduction Method
    • Long Term Nitrate Reduction
    • Vodka Method for Nitrate Reduction
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  • 02 of 07

    Controlling Nitrates With Mangrove Plants

    The key factor to controlling nitrate primarily relates to how you take care of your aquarium. At various stages in the life of a saltwater aquarium, from a newly cycled tank to a well established one, you should set up a regular maintenance care routine that is suitable for your particular system.

    Using Mangrove Plants

    The use of mangrove plants in saltwater aquarium systems to reduce and control nitrate is not a new concept by any means. This method of...MORE filtration has been around for some time, but with the popularity of wanting to find "natural" ways to take care of an aquarium, mangroves are being discovered as a good no chemicals or additives needed way to do it.

    Learn About


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  • 03 of 07

    Natural Nitrate Reduction (NNR) Filtration Setups

    The principle of NNR or Natural Nitrate Reduction filtration is that the nitrifying bacteria does all the work. The three basic NNR set ups one can choose from to reduce nitrate naturally in saltwater aquarium and reef tank systems are as follows:

    • Use live rock.
    • Use live sand.
    • Use a combination of both live rock and live sand.
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  • 04 of 07

    Using Denitrator Units, Absorption Compounds and Additives

    Denitrator Units

    Coil, flat block, and other types of denitrators are similar to the NNR setups that work on the principle that the nitrifying bacteria that grows in them does all the work. Although these units are very effective, they can be an expensive investment, but if you are a do-it-yourselfer, you can always make your own.

    Nitrate Removing Compounds & Additives

    In the...MORE quest to find quick solutions to nitrate problems, one can option to use various types of removing or absorption compounds and chemical additives to get rid of it. There are many types of products on the market that are designed to absorb nitrate, as well as other undesirable elements in aquarium water such as nuisance phosphates and silicates.

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  • 05 of 07

    Multiple Water Change Reduction Method

    Reducing or keeping nitrates in check through small partial water changes over a period of time is effective, but when the levels are dangerously high, this process cannot give you the results you immediately need. As an experiment, we allowed the nitrates in our aquarium rise to a very high level, literally off the scale, and then performed a multiple step water change procedure that we had contemplated trying out for some time. We found it to be very efficient, quickly lowering the nitrates to...MORE zero in a day. Rapid nitrate reduction is said by some aquarists to be just as harmful to the tank inhabitants as the high nitrates themselves, but we experienced no ill affects in this regard. In fact, it worked so well for us the first time that we use this multiple step water change procedure whenever we make a water change. If ill affects of rapid nitrate reduction are a concern, you can do this type of water change over a longer period of time, rather than all in one day.

    Closing Comments

    The methods for controlling nitrates in your saltwater aquarium system we have discussed here are just a few to take a look at. Nitrate control isn't really as hard as you might think. Consider regular aquarium maintenance care first. If that doesn't work, pick a nitrate control method and give it a try. If after a while you do not get the desired results you are looking for, try another one, and keep trying until you find one that works for your system.

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  • 06 of 07

    Long Term Nitrate Reduction

    Another reliable, but heretofore unheralded method in the saltwater aquarium hobby is the use of the combination of Hiatt's Right Now! (RN!) bacteria and a quantity of activated carbon (we used Hiatt's Tri-Based Pelletized Carbon (TBPC) with great success) in the tank's filtration system. (See the results in "New Biological Filtration For an LFS - 1,000 Gallon System" and "New Biological Filtration For an LFS - 3,500g Shark Tank"). There is a specific bacteria strain...MORE in the RN! which reacts with Nitrates and an element in the TBPC, converting the nitrates into Nitrogen gas, which is then vented into the atmosphere via the water's surface.

    Read more about Long Term Nitrate Reduction.

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  • 07 of 07

    The Vodka Method For Nitrate & Phosphate Reduction

    The "Vodka Method for Nitrate Reduction" uses the same principle as the "Long Term Nitrate Reduction". However, instead of using activated carbon for the carbon source, it utilizes the organic carbon found in alcohol. As Charles Delbeek explained it: "the "vodka method" is a means to add inorganic carbon in the form alcohol to cause bacteria to grow. In boosting bacterial growth, nitrate and phosphate are incorporated by the bacteria, lowering these values in the...MORE water. The excess bacteria are then either removed through skimming or are consumed by other organisms, such as sponges."