KH, or carbonate hardness, is important in all aquariums, but particularly in a reef aquarium - without sufficient KH, proper skeletal formation in invertebrates cannot take place. KH is directly related to the alkalinity and buffering capacity of your water, and alkalinity should not fluctuate by more than 5% from the optimum level of approx. 2.8 meq/L - a maximum fluctuation of 0.14 meq/L. Salifert's KH/Alkalinity test kit is sensitive enough to detect small changes in levels of alkalinity, measuring in steps of 0.1 meq/L and demonstrating a very sharp color change.
Natural sea water has a KH of 8 dKH or alkalinity of 2.9 meq/L. The reagent contains a dye; avoid spilling on fabric or other materials or they may be stained.
Using the 5ml syringe add 4 ml of aquarium water in the test vial. For a lower resolution and more tests per kit add 2 ml instead of 4 ml.
Shake the KH-Ind dropping bottle a few times and add 2 drops in the test vial (1 drop for the low resolution mode).
Put the plastic tip firmly on the 1 ml syringe. Draw up the KH reagent (ensure that the tip of the plastic tip is constantly submersed in the reagent) until the lower end of the black part of the piston is exactly at the 1.00 ml mark. There will be some air just below the piston; this will not influence the test result.
Add the KH reagent by drops from the 1 ml syringe to the water in the test tube. Swirl after each drop a second or two. Continue with this until the water changes from blue/green to a orange/red or pink color (whichever color is observed first).
Hold the syringe with the tip facing upward and read the position of the, now upper end, of the black part of the piston. The syringe has graduations of 0.01 ml.
Read the KH or alkalinity value from the table (included with the test kit) or calculate as follows: KH in DKH = reading from step 5 x 16.
Alk in meq/L = reading from step 5 x 5.71.
If you have chosen the lower resolution multiply the calculated result by 2.