In 1995 the biological nature of anammox was identified. Labeling experiments with in combination with showed that 14-15 was the dominant product making up 98.2% of the total labeled . It was realized that, instead of nitrate, nitrite was assumed as the oxidizing agent of ammonium in anammox reaction. Based on a previous study, Strous et al. calculated the stoichiometry of anammox process by mass balancing, which is widely accepted by other groups. Later, anammox bacteria were identified as planctomycetes, and the first identified anammox organism was named "Candidatus" "Brocadia anammoxidans."