Measure Carbonate Hardness/Alkalinity in a Reef Aquarium

The carbonate hardness (KH) or alkalinity* of a water sample characterizes the buffering capacity, i.e., the ability to maintain the pH value of the water. It is primarily defined by the proportion of hydrogen carbonate ions in the water. As the pH value increases, other basic ions, such as the hydroxide ions, also contribute to the alkalinity. The alkalinity should be tested in all aquariums regularly. If the alkalinity in the aquarium is too low, the pH value can sink (sudden drop in acidity) to a level that is life-threatening for many fish and invertebrates. In reef aquariums, adequate alkalinity is essential for strong coral growth. On the other hand, overly high alkalinity in saltwater tanks can lead to lime precipitates and negatively impact coral growth.

*Water chemistry uses many terms to describe the buffering capacity with varying definitions. The term “carbonate hardness” is customary in reef and fishkeeping; however, it is the alkalinity that is measured. In this test, both terms are used synonymously. The reading for alkalinity is usually given in degrees of German hardness (°dKH). You can find a table for converting this unit into other common units (such as the equivalence unit millival per liter (mval/l) or the volume of a substance in mmol/l) on the second cover page.

Natural seawater has an alkalinity of 6.5 °dKH. The alkalinity in saltwater aquariums should range from 6 to 9 °dKH.

Ask your retailer for the correct alkalinity for your tank.

How to correct unfavorable values:
To increase the alkalinity when levels are too low, we recommend using Fauna Marin Carbonate MIX or Fauna Marin Easy dKH.

Contents of package:

• 10 ml / 0.34 fl.oz. of reagent A
• 50 ml / 1.69 fl.oz. of reagent B
• 1 glass cuvette 10 ml
• 1 dosing syringe 5 ml
• 1 dosing syringe 1 ml with the dropper tip
• 1 instruction for use

In order to protect the environment, the reagents for the KH Alkalinity Test are also available in affordable refill packs!

Safety Note: 

Flammable liquid and vapor. Keep away from heat, sparks, open flames, hot surfaces. No smoking. Keep out of reach of children.