The Tetra test strips enable you to quickly and reliably determine the six most important water values in aquariums in one simple step: dip the test strips into the water, swirl them in the water for one or two seconds, shake off any excess water and read off the most important information about the water values just 60 seconds later. The colour chart can be used to determine whether these are within the safe range. The pH, general and carbonate hardness (GH + KH), nitrite (NO₂^-), nitrate (NO₃^-) and chlorine (Cl₂) in the aquarium water are measured. Aquarium inhabitants such as fish react very sensitively to excessive changes in the pH value, which impacts their well-being. The general hardness affects the vital functions of fish, while the carbonate hardness has a direct influence on the stability of the pH value (pH buffer). The test strips also measure the nitrite and nitrate values of the aquarium water. Nitrite is extremely harmful, even in very low concentrations, and should not be detectable in the water. Nitrate is a nutrient that helps plants to grow. However, excessively high levels of NO₃^- can be harmful to fish and promote excessive algae growth. Chlorine may also be present in the water, and is harmful to fish and plants. Just like nitrite, chlorine should not be detectable in the aquarium water. The Tetra Aquatics app can be used to determine the water values quickly and reliably using a smartphone.