The Tetra Test Nitrate Water Test Kit is a simple to use testing kit for determining Nitrate (NO3) levels in freshwater aquariums, marine aquariums and ponds. The Tetra Nitrate Test Kit provides readings between 0 mg/l and 100 mg/l. Organic nitrogenous substances in the water, such as fish excreta and food remains, are decomposed in various stages via the Nitrogen Cycle: from harmful Ammonia, into toxic Nitrite and finally into Nitrate. Nitrate is a plant nutrient which is nevertheless increasingly harmful to fish in concentrations exceeding 50 mg/l, and encourages tiresome algae growth. Application:The Tetra Test Nitrate Water Test Kit is a simple to use kit for determining Nitrate levels. It is a liquid kit, which works by changing the colour of a water sample in relation to the Nitrate concentration. You simply need to compare the colour of the sample to the easy-to-read colour chart in order to determine the Nitrate level. Tetra recommend testing the Nitrate level every 1-2 weeks. Always read the instructions carefully before use. This test kit is compatible with the Tetra Digital Water Test App available for most smart phones and tablets. Once you have tested the water, the app will suggest the appropriate product. Simply download the free app!