The Tetra Test Nitrate NO3 accurately and reliably measures the nitrate levels in aquarium and pond water. Nitrogen-containing organic substances, caused by leftover food and fish waste, are broken down in the water through various stages, leading to harmful ammonia (NH3), toxic nitrite (NO2), and problematic nitrate (NO3). While nitrate is beneficial for plant growth, excessive nitrate in aquarium or pond water becomes harmful to your fish when levels exceed 50 mg per liter, and algae growth can increase uncontrollably. It offers good long-term stability and a high range. Suitable for freshwater and saltwater aquariums as well as ponds.