Ammonia, Ammonium

Ammonium (NH4+) — or its uncharged form ammonia (NH3) — is a form of nitrogen which aquatic plants can absorb and incorporate into proteins, amino acids, and other molecules. High concentrations of ammonium can enhance the growth of algae and aquatic plants. Bacteria can also convert high ammonium to nitrate (NO3-) in the process of nitrification, which lowers dissolved oxygen.

Ammonia in water is either un-ionized ammonia or the ammonium ion.  Typically, the value reported is the sum of both forms and is reported as total ammonia or simply - ammonia.  The relative proportion of the two forms present in water is highly affected by pH.

Ammonium | pH of Ammonium | Ammonia vs Ammonium

Un-ionized ammonia is the toxic form and predominates when pH is high. The NH4+ ion is relatively non-toxic and predominates when pH is low. In general, less than 10% of ammonia is in the toxic form when pH is less than 8.0 pH units. This proportion increases dramatically as pH increases.

The equilibrium between NH3 and NH4+ is also affected by temperature. At any pH, more toxic ammonia is present in warmer water than in cooler water.

The YSI ammonium sensors consist of a silver/silver chloride wire electrode in a custom filling solution. The internal solution is separated from the sample medium by a nonactin membrane, which selectively interacts with NH4+ ions.

Essential Ammonia Posts on the Blog

Pond Based Aquaculture | Understanding Ammonia

Which Water Quality Handheld Instrument Do I Need? | We Have the Answer

Myths and Realities: Ammonium Based Aeration Control in Wastewater

Ion Selective Electrode Measurement - Fundamentals in Online Analysis

Ammonia in Water - YSI Knows ISE's

Ammonia measurement in water.

Featured Ammonia Products

EXO2 Multiparameter Sonde

Multiparameter Water Quality Sonde for Unattended Monitoring (7 sensor ports, including a central wiper port)

Request Pricing

TruLab pH/ISE 1320

Dual channel benchtop pH/ORP/ISE instrument


ProDSS Multiparameter Digital Water Quality Meter

The Ultimate Sampling Handheld. Portable Meter for DO, Conductivity, Salinity, TDS, pH/ORP, Turbidity, Algae, Temperature and more

$2,053.50 - $2,701.50

IQ SensorNet AmmoLyt® Plus Sensors

Ammonium and Potassium probe for IQ SensorNet system

Request Pricing

IQ SensorNet Alyza Analyzer NH4

IQ SensorNet Analyzer for Ammonium

Request Pricing