Shake reagent bottle well before using! Do not allow tested water to contact aquarium or pond water! 
1. Rinse the measurement vial several times with the water to be tested, then fill to the 5 ml mark. Dry the vial on the outside. 2. Add reagent drop by drop. Shake vial gently after every drop, until the color changes from red via brown to green. 3. The number of drops used from the reagent represents the existing total hardness (in °dGH). E.g., 5 drops = 5°dGH. 4. Cleaning: Clean the vial thoroughly with tap water before and after each test. Close reagent bottle immediately after use. Store at room temperature and away from light. Keep locked up and out of the reach of children. For testing ornamental fish aquariums and pond water only. 

US Information for use Most ornamental fish originate from countries where the soil is poor in minerals. However, it is exactly the opposite in many other areas around the world. Rain water dissolves calcium and magnesium from the soil and consequently creates hard water. With the sera gH-Test, you can quickly determine the exact total hardness. Looking at the natural conditions helps selecting the optimal fish stock for a community aquarium, and is a precondition for successful breeding. High total hardness levels can be lowered by mixing in R/O water. A combination of sera aquatan and sera blackwater aquatan or filtering through sera super peat will create soft water, as required for most South American fish (e.g. from the Amazon basin).