Quick measurement in seconds - The Dennerle Water Test 6in1 is an instant test for the six most important water parameters: pH value, carbonate hardness, total hardness, nitrite, nitrate, and chlorine. In just 60 seconds, you will know the water quality of your garden pond. It is especially recommended for new ponds, new or increased fish stock, algae problems, water changes, filter cleaning, prolonged rain, treatment with remedies, or noticeable fish behavior. Recommendation: measure one to two times per week.