Nitrite and Nitrate in RAS

When considering the application of real-time monitoring of nitrite and nitrate in recirculating aquaculture systems, varying salinity is a major consideration. Fully saline RAS are common and represent a significant portion of RAS globally. In addition, within freshwater RAS, the salinity of the water can change considerably over time due to the addition of seawater or NaCl. For these reasons, monitoring of nitrite and nitrate in RAS has been challenging and often inaccurate.

Other analytical methods or commercially available analysers cannot effectively measure nitrate and or nitrite in-situ within RAS. The AquaNOx® analyser is uniquely unaffected by varying salinities.

For the first time, accurate real-time in-situ monitoring of nitrite and nitrate across all RAS is possible through the Aquamonitrix® analyser. The way in which the accuracy and precision, delivered by AquaNOx®, is unaffected by varying salinity is demonstrated in figures below. Despite salinity ranging from freshwater to fully saline, accuracy remains >95% and precision is ± 5%. The raw chromatograms generated by the analyser are also shown, highlighting the fact that selective and robust detection of nitrite and nitrate is achieved despite fluctuating salinity.

Salinity Independent measurement NO2

Demonstration of the analytical robustness of the Aquamonitrix® analyser to varying salinities over 500 runs. Using one single calibration which is performed in factory, the analyser can accurately detect nitrite and nitrate in varying salinities.

Salinity Independent measurement NO3

Chromatograms salinity independent analysis of NO2 and NO3


AquaNOx® enables real-time accurate measurement of nitrite and nitrate in RAS and adds value across both freshwater and fully saline RAS applications. This real time data allows for improved understanding of biofilter at start-up phase and through production, the potential for improved estimation of maximum feeding rates and identification of excess feeding, and a greater understanding of water quality, reducing the risk of mass mortalities due to nitrite poisoning.>