Instructions
Purchase a water hardness test kit at the Aquatic House website (see Resources). You may go to any pet store offline also and ask the sales representative for a GH and KH test kit for water hardness.
Open the test kit. There will be two vials of liquid; one will read GH and the other KH.
Prepare for the water test. Look in your kit and find the empty tube. Fill this with aquarium water. Place the tube into the aquarium and scoop water into it.
Look at the tube. If the water is higher than the test line on the tube, pour out the excess water. Now take the vial marked GH and open it. There is an eyedropper in the bottle. The package directions will state how many drops you need for the test.
Drop the correct number of drops into the test tube and look at the results. The test tube is calibrated to show you the safe zone or if the GH is too high or low.
Take the other empty tube and fill it with aquarium water. This time you will test for KH by dropping the correct number of drops from the KH vial into this test tube.
Check the results. If your water hardness is too high or too low, then respond appropriately and retest until your aquarium water is safe for your fish.
How to Test Aquarium Water for Water Hardness
Fish are sensitive creatures that only survive in certain conditions. One of these conditions is water hardness. Water hardness is comprised of two parts, general hardness, or GH, and temporary or carbonate hardness, called KH. Test your aquarium water for these qualities to keep your fish happy and healthy.