Carbinate Hardness or General Hardness?

[lildraken]

I've been measuring my water hardness with a KH test kit. I realized that there's also a GH test kit. Do I need to measure both? I've read the articles on what water hardness, but is the difference between the two not very significant? I don't know what to use!

[jdieck]

Just use the KH one, all our parameters on alkalinity refer to carbonate alkalinity.

[Randy Holmes-Farley]

General hardness is used in freshwater, but in seawater is a huge number, that includes calcium and magnesium added together, and is not especially useful.

from this article:

The Units of Measure of Reefkeeping
http://reefkeeping.com/issues/2005-08/rhf/index.php


GH (general hardness)

Hardness is a characteristic of water due to the presence of dissolved calcium and magnesium. Water hardness is responsible for most scale formation in pipes and water heaters (calcium and magnesium carbonates, typically), and forms insoluble solids when it reacts with soaps. Hardness is often expressed in grains per gallon, parts per million or milligrams per liter, all as calcium carbonate equivalents. It is a measure often used in freshwater aquarium systems, but not often in marine systems, where its values are very large. Seawater has a total (general) hardness of about 6.3 g/L (6,300 ppm) of calcium carbonate equivalents. These linked articles detail aspects of magnesium and calcium in seawater.