Sera Ammonium/Ammonia Test- NH4/NH3 for the exact determination of the ammonium/ammonia content in fresh or marine water. The test is sufficient for approx. 50 tests. Useful bacteria convert nitrogen-containing waste products into ammonium or ammonia. The sera ammonium/ammonia-test tells you the overall concentration of ammonium and ammonia. The actual concentration of toxic free ammonia is easy to calculate from the measured level and the pH value by means of the enclosed calculation chart.