sera nitrate-Test (NO3) Freshwater, Marine water,PondWater, Testing Care For easy determination of the nitrate content in fresh and sea water Nitrate (NO 3 ) is an indicator of high organic pollution. The source of the organic pollution should be eliminated; a partial water change provides an acute remedy. Filtering through sera siporax Professional helps in the long term to avoid nitrate accumulation. Sufficient for approx. 60 measurements.