Instructions
Clean one of the provided test tubes with soap and water and allow it to dry completely before you use it. Any leftover water in the tube from cleaning could change the outcome of the test. Rinse out the tube with the aquarium water; then fill it with the same water up to the "Fill" line.
Turn the carbonate hardness test solution bottle upside down and squeeze it to add one drop to the water in the test tube. The first drop will turn the water deep blue. Place the cap on the test tube and flip it over several times to mix up the solution. Do not cover the top with your finger as this could change the results.
Let the water settle and watch it for a few seconds. If the water does not change from blue to yellow, uncap the test tube and add one more drop of the testing solution to the tube. Place the cap on the tube once again and flip the tube over several times to mix the water inside.
Continue adding drops of the solution to the test tube using the above method until the water turns yellow after adding a drop and mixing the water. Keep track of the number of drops that it takes for the water to turn colors. The number of drops you used is the carbonate hardness level of the water in your aquarium.
How to Use an API Carbonate Hardness Test Kit
If you have an aquarium in your home with many fish swimming around inside, it is important to keep the proper balance of chemicals in the water to keep the fish healthy. Low levels of carbonate hardness, also known as KH, can cause rapid PH shifts in the water which can harm your fish. An API Carbonate Hardness Text Kit measures the KH level in your water to help you make adjustments if necessary.