API GH & KH Test Kit

Since adding tap water increases the hardness of aquarium water, frequent GH and KH testing is imperative.
This kit measures both general hardness (GH) : the measure of calcium and magnesium in water, and carbonate (KH) hardness : the measure of carbonate and bicarbonate concentrations
Proper GH and KH levels are an important part of water quality and are necessary for the health of fish and the development and growth of aquarium plants

Kit contains:

• : Two Dropper bottles for accurate dispensing of test solutions
• : Easy-to-read instructions and colour chart
• : Non-staining glass test tube with snap-tight cap

Q: What is "Water Hardness"?
A: General Hardness or GH is the measure of calcium (Ca++) and magnesium ions (Mg++) dissolved in water. General Hardness is measured with the GH Test Kit. Carbonate Hardness, also known as KH, refers to the concentration of bicarbonate (HCO3-) and carbonate (CO3--) dissolved in water. Carbonate Hardness is measured with the KH Test Kit.

Calcium and magnesium carry a positive charge and form "ion pairs" with negatively charged ions like bicarbonate, forming calcium bicarbonate and magnesium bicarbonate; Ca(HCO3)2 & Mg(HCO3)2.

Marine reef aquarists interested in measuring the calcium level in their aquariums should use a calcium test kit made specifically for this purpose. The KH Test Kit can be used to test the carbonate hardness in saltwater aquariums.
Q: How do I test for water hardness?
A: GH and KH are easily measured with the GH & KH Test Kit. This kit measures GH and KH in German degrees (° dGH & ° dKH) and parts per million (ppm). Some aquarium literature refers to water hardness in degrees while others use ppm. Your aquarium water may have a high GH and KH, low GH and KH, or a situation where one type of hardness is high and the other low, i.e. low GH & high KH. If, for example, you have a water softener on your tap water supply the GH will be zero (or very low) while the KH, which is not removed by a water softener, will remain high.

In marine aquariums the KH is supplied by the synthetic seawater mix used to make saltwater. The KH level will depend on the particular brand of salt.
Q: What effect does water hardness have on the aquarium?
A: Water with a GH will contain a lot of calcium and/or magnesium. This is great if you are keeping African cichlids or other fish that like hard water. While excessive GH is not dangerous to tropical fish, many species come from water with a GH level of 35-ppm to 90-ppm (2-5° dGH). Most aquatic plants also prefer a GH level of 35-ppm to 90-ppm (2-5° dGH). Excess GH also contributes to white scale build-up on the aquarium lid and light fixture. As aquarium water evaporates calcium and magnesium (and other minerals) are left in the water causing GH to rise over time. Lowering GH (softening) has no effect on pH. Reducing the GH level does increase the effectiveness of Proper pH buffers (freshwater).

KH is important in relation to pH. KH, also known as alkalinity or buffering capacity helps stabilize the pH in the aquarium. Carbonate and bicarbonate ions give water its ability to resist increases or decreases in pH. Water with very low KH may experience wide fluctuations in pH because the buffering capacity is low. A high KH level indicates that the pH will be very stable. High KH is almost always associated with a high pH. This is not the case, however, when Proper pH buffers are added to freshwater aquariums. Proper pH products are true buffers. They will raise or lower pH to reach the pre-set pH level. Proper pH 7.0, for example, increases buffering capacity (KH) at pH 7.0. This means the buffering capacity is strong specifically at pH 7.0. The pH is "locked in" at 7.0.

KH can be adjusted in marine aquariums with Proper pH 8.2. Proper pH 8.2 increases KH by adding a blend of carbonate and bicarbonate buffers to the water. This adjusts the pH to a level of 8.2 to 8.4 depending on the existing buffer provided by the synthetic salt formula. Many marine aquarists try to maintain a KH level around 140 to 178-ppm (8 to 10 ° dKH).
Q: How does KH affect pH adjustments?
A: Carbonate hardness directly affects the ease of making pH adjustments. In freshwater a high KH level makes lowering the pH very difficult. Each time a pH adjuster is added some of the KH is "neutralized". Each consecutive dose reduces the buffering capacity (KH) of the water. The pH will not go down, however, until the "breakpoint" is reached. When the breakpoint is reached the KH is sufficiently reduced to allow the pH to go down. This is why it may take several doses of aquarium pH adjusters to successfully lower the pH. Adjusting the pH is much easier after the KH has been reduced. Maintaining the pH once adjusted can be difficult with tap water having a high KH level. Every time tap water is added more KH is added to the aquarium. This shifts the water chemistry toward a higher pH level. Some aquarists use distilled water to replace evaporated water. Other kinds of bottled water like spring water are usually high in minerals and will increase water hardness. The Tap Water Filter will remove all minerals and pollutants from tap water, permitting easy adjustment of pH and water hardness.