Hardness Test Kit

The NT Labs Hardness Test Kit provides a simple, easy to use testing kit for determining GH and KH  levels in ponds and freshwater aquariums. The NT Labs Hardness Test Kit comes complete with test tube and liquid reagents to provide accurate results for up to 80 tests.

What is KH?
KH, also known as “total alkalinity” or “carbonate hardness”, is a measure of the buffering capacity of the water in your pond or aquarium. The buffering capacity refers to how well it can resist changes in pH.

What is the correct KH level?
This test kit measures KH in dKH (where one dKH = 17.8 ppm as CaCO3). It is essential to maintain a minimum KH level of at least 4 dKH at all times. A KH of between 6 and 8 dKH is more desirable.

What do I do if the KH level is wrong?
Check the KH level of your tap water. If the level is above 6 dKH, then regular water changes should keep the KH value in the pond topped up at a reasonable level. If the KH value of your tap water is below 6 dKH, you will need to add a KH buffer such as NT Labs KH Buffer Up to your pond or NT Labs Aquarium KH Up - PH Stabiliser for an aquarium.

What is GH?
General Hardness is a measure of the total amount of minerals dissolved in the water. Water hardness lies on a spectrum between ‘soft water’ or ‘hard water’ depending on the amount of dissolved minerals: the more minerals present, the greater the hardness. Hard water is responsible for the build-up of limescale.

What is the correct GH level?
This test kit measures GH in dGH (where one degree = 17.8 ppm as CaCO3). For pond fish, between 8 and 12 dGH is ideal whilst for aquarium fish the correct GH depends on the type of fish being kept. For soft water species, aim for a GH of around 3 to 6 dGH, whist for hard water species, 10 to 15 dGH is the correct range.

What do I do if the GH level is wrong?
Test the GH of your tap water. The GH of tap water is determined by whether you live in a hard or soft water area. If the water is too hard for the fish being kept, alternative waters can be used, such as reverse osmosis water, to lower the GH. In ponds, where rainwater tends to lower the GH with time, NT Labs GH Minerals Up can be used to boost the GH back to a suitable level. To increase the GH in an aquarium, calcium carbonate rocks (like ocean rock) can be used to provide a continual source of GH minerals.