When keeping freshwater fish and plants, the General Hardness (GH) and Carbonate Hardness (KH) of aquarium water should match their natural habitat. Adding tap water may increase water hardness. Use this kit to easily and accurately measure both GH and KH.

Why Test for KH (Carbonate Hardness)& GH (General Hardness)?
Tap water rarely provides the water conditions necessary to maintain an optimal aquarium. Some tap water supplies have very low KH (below 3 ºdKH) which has very little pH buffering capacity. This can contribute to wide pH swings in the aquarium. Also, when water evaporates, it leaves behind hardness ions. Topping off with tap water simply adds more minerals to the aquarium, resulting in a steady increase in GH. It is therefore necessary to test the GH and KH frequently to monitor water quality and prevent stressful conditions from occurring.

Directions for Testing KH

1. Rinse a clean test tube with water to be tested.
2. Fill the test tube with 5 ml of water to be tested (to the line on the tube).
3. Holding the bottle vertically, add KH Test Solution, one drop at a time. Be sure to count the number of drops being added.
4. Cap the test tube and invert several times after each drop.
5. The test is completed when the water in the test tube, after having been shaken, turns from blue to yellow. If you have difficulty discerning the color after the first drop of test solution is added, remove the cap from the test tube and, while holding it over a white background, look down through the tube.
6. The KH value is determined by the number of drops of test solution that must be added to turn the water in the test tube bright yellow.

Directions for Testing GH

1. Rinse a clean test tube with water to be tested.
2. Fill the test tube with 5 ml of water to be tested (to the line on the tube).
3. Holding the bottle vertically, add GH Test Solution, one drop at a time. Be sure to count the number of drops being added.
4. Cap the test tube and invert several times after each drop.
5. The test is completed when the water in the test tube, after having been shaken, turns from orange to green. If you have difficulty discerning the color after the first drop of test solution is added, remove the cap from the test tube and, while holding it over a white background, look down through the tube.
6. The GH value is determined by the number of drops of reagent that must be added to turn the water in the test tube green.

What the Test Results Mean
Use the table below to create the ideal water hardness levels for your aquarium fish. When keeping a community aquarium with a variety of tropical fish, adjust the GH and KH to 3 - 6º (50-100 ppm).

Adjusting KH
Partial water changes can be used to decrease KH. Use the API TAP WATER FILTER to make deionized water and reduce KH to a desirable level. To increase KH use API PROPER pH™ buffers. PROPER pH 6.5, 7.0 and 7.5 are non-carbonate buffers that automatically adjust pH and increase KH. API PROPER pH 8.2 is a carbonate buffer suitable for marine and African Cichlid aquariums. Adjusting GH in Freshwater GH can be lowered with API WATER SOFTENER PILLOW, which removes calcium and magnesium ions. Also, partial water changes with deionized water will gradually reduce GH to the desired level. API ELECTRORIGHT will increase GH.

This kit contains the following:

• 1 x 37 ml GH Test Solutions in liquid dropper bottle with child-resistant safety cap
• 1 x 37 ml KH Test Solutions in liquid dropper bottle with child-resistant safety cap
• Easy-to-read instructions
• 2 x Test tubes with snap-tight cap