How to Reduce High Toxic Nitrates Quickly & Efficiently

  • High nitrate accumulation, sometimes referred to as old tank syndrome, can be a common problem for long time aquaria keepers. It usually occurs when regular maintenance and water change routines are ignored. As an experiment, we allowed our tank nitrates to rise to a dangerously high level, literally off the scale, to observe the transitions the tank would go through. The experiment was successful in that it allowed us to observe the formation of the different algae.

    When our experiment was over, we decided to try out this instant nitrate reduction water change method that had been contemplated for some time. Performing the water change method shown in the animated graphic below, we reduced our nitrates quickly to zero with no ill or harmful effects to any of our established aquarium residents; a 15″ Snowflake Eel, some various types of hermit crabs and snails, a few crabs, two colonies of Zoanthid, some non-living corals, and some live rock.

    The behavior of the tank inhabitants improved greatly afterward as well. They became more active, started eating better, and had brighter colors within a few days. We even added a new mated pair of Coral Banded Shrimps the day after completion of the water change procedure, with no problems at all.

    One important consideration before you start a massive (or any, for that matter) water change is to remember that you will also be changing the pH in your tank (probably upwards). Before beginning a water change, it is wise to slowly adjust your tank water pH to where it will be when you are finished. This will prevent your tank critter from going through “pH shock”, which can be fatal to more sensitive tank critters.

    Prior to beginning your water change, you can adjust the pH upward with common baking soda, or downward with one of the many products on the market to reduce the pH of aquarium water.

    Animated Graphic of Rapid Nitrate Reduction

    animated gif of Rapid Nitrate Reduction
    Graphics by Stan Hauter

    Many people try to reduce their nitrate levels by performing a series of partial (20%) water changes. This will reduce your nitrate (or any other chemical substance) levels, but it is rather inefficient if the object is to reduce the levels to near zero in the shortest period of time as possible, with the least amount of water. On the other hand, if you reduce the level of water in the tank to 20% of normal and then refill the tank to a 40% level, you have already reduced your nitrate levels by half.

    If you then refill the tank to the 100% level, your nitrate levels will be 20% of the original level that you started out at. If, on the other hand, you reduce the 40% water level once more to 20% and then refill the tank, you will end up with a nitrate level of 10% of what you started with. Perform the 40% to 20% reduction once more, and you will end up with a nitrate level of 5% of what you started with. Just think about it for a minute. If you started out with a nitrate level of 100 ppm and used this method, your 100 ppm nitrates would be reduced, in a short period of time, to 5 ppm, which is considered, by most, to be an acceptable level even for corals.

    Yes, It Really is Safe

    Fish tank
    Moto “Club4AG” Miwa/Flickr/CC By 2.0
    Some people have expressed concern that the rapid reduction of nitrates would “shock” the tank critters. This is an understandable concern, but under the circumstances wouldn’t you think that the rapid reduction of potentially harmful toxins in a tank to be of the utmost importance, and a lot less harmless? It would be like standing in a closed garage with a car engine running, filling the garage with carbon monoxide, and someone telling you not to open the garage door; that the rapid reduction in carbon monoxide levels would in some way be more harmful to you than only reducing their levels by 20%. If it was me in that situation, I would kick the door open as far as it would go.To avoid the urgent need to have to reduce high toxic nitrate levels, it is much easier to following regular maintenance and water change routines. If you are in a position where everything you have tried does not seem to work and your nitrates continue to be a problem, you might try this water change method out.

    We wanted to see what the results and effects would be of performing this water change process as quickly as possible. No problems resulted. However, if you are concerned about “shocking” your tank inhabitants, you can always perform this process over a period of time (waiting a few days between each water change process) until the nitrates are reduced.

Leave a Comment