In aquariums and fish farms, you need to be able to differentiate between Carbonate Hardness (KH) and Total Hardness (GH).

Carbonate hardness (KH or CH) refers to the ability of the water to maintain a stable environment and subsequently, the health of fish. The carbonate hardness is the 'buffering' ability of the water. To determine this on a photometer you need Palintest Alkalinity tablets, known as Alkaphot (part code AP188).

General hardness (GH) refers to the 'hardness' of the water caused by calcium and magnesium ions. Different aquatic species prefer different environments, some prefer 'hard' water and some prefer 'soft' water. The hardness of your water is often dictated by the source of the water. If it's from groundwater it tends to be harder, if it's from surface water it tends to be softer. To determine this on a photometer you'll need our Hardicol reagent (part code AP254).

Sometimes the units dH are used. This means "degrees hardness''. Most test kits define results in terms of ppm CaCO3 means 'parts per million equivalent to that of calcium carbonate' - it doesn't mean that the hardness is in this form.

1 unit dH equals 17.8 ppm as CaCO3.

To order your reagents to test your aquarium, browse our range of instrument platforms in the Photometers section, and view the relevant reagents for these tests.