API KH Carbonate Hardness Test Kit for freshwater & saltwater

Tests tap water & fresh or saltwater aquariums for carbonate hardness (KH). 

Can be used to determine the proper dose of pH buffers.

What is Carbonate Hardness?
Carbonate hardness (also known as alkalinity) is the measure of carbonate and bicarbonate ion concentrations dissolved in water. These minerals are present in municipal, well, and bottled spring water. The level of carbonate hardness in tap and bottled water depends on the source of the water and the treatment processes it has undergone. Carbonate hardness helps stabilize pH in the aquarium. An aquarium with a low kH level (50 ppm or less) will tend to be acidic. Aquariums with very low kH are subject to rapid pH shifts.

Directions for Testing Carbonate Hardness (KH):

  • Read thoroughly before testing. Do not allow test solution to get into aquarium. 
  • To remove childproof safety cap: With one hand, push red tab left with thumb while unscrewing cap with free hand. 

1.Rinse a clean test tube with water to be tested.
2.Fill the test tube with 5 ml of aquarium water (to the line on the test tube). 
3.Add carbonate hardness test solution, one drop at a time, holding dropper bottle upside down in a completely vertical position to ensure uniformity of drops. After first drop is added, solution will turn blue.
4.Cap the test tube and invert several times after each drop. Keep count of the drops being added. Do not hold finger over open end of the tube as this may affect the test result. 
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 carbonate hardness value is determined by the number of drops of the reagent that must be added to turn the water in the test tube to bright yellow.


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