WHAT IS CARBONATE HARDNESS
A Carbonate Hardness test is a test of the carbonate and bicarbonate extent contained in a sample of water. It affects all aquaria, both salt and fresh. It is called many names, according to the jargon of an industry or country of origin of the test kit.
CARBONATE HARDNESS = ALKALINITY=kH(German) =ACID BINDING CAPACITY.

The units used to measure Carbonate Hardness depends on the name of the Test Kit. For instance, if the Test Kit is called Alkalinity, the test would be measured in milliequivalents. kH test kits usually use dH (German) and Carbonate Hardness is usually measured in ppm (parts per million).
(10//ppm = 1 meq/1 = 2.8dH (German).

STABILITY OFpH
The Carbonate Hardness of water is an important measurement, both in freshwater and marine because the level of Carbonate Hardness is the basis for the value of the pH in a given sample of water. A strong Carbonate Hardness reserve in water can mean a very stable pH and the bonus of an alternative supply of carbon dioxide for plants and algae if supply runs short in an aquarium. This applies equally for marine or freshwater aquaria.

Freshwater aquariums are recommended by German literature to have between 85ppm to 170ppm Carbonate hardness, while, in marine aquariums, the minimum is 125ppm with a recommended maximum around 250ppm. Sea water has a natural Carbonate Hardness of 125ppm.

DEPLETION OF THE CARBONATE HARDNESS RESERVE
Acids which form as a result of the breakdown of waste products by bacteria (via biological filtration) is the most common way the carbonate hardness reserve is depleted. As a carbonate hardness reserve is depleted, the pH drops. In aquariums with no carbonate hardness the pH is very unstable. An example might be:- the pH may be adjusted to 7.00 in a freshwater aquarium with a reasonable stock load, but because the carbonate hardness is low (less than 20ppm) the pH falls rapidly overnight and by the next day has again turned acid.

CARBONATE HARDNESS AND PLANTS.
A low Carbonate Hardness usually has a negative effect on the growth of plants. While a strong Carbonate hardness (around 100ppm) has a positive effect. This is evident in the strong plant growth in streams that flow from limestone terrain. This natural phenomenon may be recreated in aquaria by strong water movement and manipulation of the carbonate hardness level.

CARBONATE HARDNESS AND INVERTEBRATES.
While marine fish seem to be little affected by a temporary low carbonate hardness and the resulting low pH, most invertebrates can be seriously affected, some irreparably. Live corals appear to do better in aquaria when carbonate hardness levels are above the natural level of 125ppm. Carbonate hardness at levels above 125ppm seem to aid the Zooanthellie algae living symbiotically with the coral and also may aid hard corals in extracting calcium from sea water.

RAISING CARBONATE HARDNESS IN MARINE SYSTEMS.
Use Aquasonic kH-UP Carbonate Hardness generator tablets. 1 tablet per 120L raises the carbonate hardness by approx.20ppm. No adjustments to pH are necessary. The tablets, which take up to 24 hours to dissolve, are best used by placing them in the filter chamber. Monitor carbonate hardness levels with an Aquasonic Carbonate Hardness Test Kit.

STABILISING pH IN FRESHWATER AQUARIUMS
To stabilise the pH in freshwater aquariums, the carbonate hardness needs to be raised to levels above 60ppm with recommended levels around 90ppm. This is achieved easily with Aquasonic kH-UP Carbonate Hardness generator tablets. 1 tablet raises the carbonate hardness of 120L of water by approx. 20ppm. The tablets dissolve within 24 hours. Monitor the carbonate hardness, with an Aquasonic Carbonate Hardness test kit, daily until the desired level is obtained. As the carbonate hardness level rises, so too will the pH.

pH ADJUSTMENT
METHOD (A)
The pH may be adjusted down to a desired level with Aquasonic "pH-LOWER". Dose rates are 5ml per 20L. Wait for 12 hours to allow complete mixing then re-test the pH to determine if re-dosing is necessary. It is recommended that the pH be set at around 7.0 to 7.2. This process of raising the carbonate hardness and then setting the pH, will form a buffer which will hold the pH stable. This stability will last until the carbonate hardness reserve is depleted, of course regular additions of "kH-UP" tablets will replenish the carbonate hardness reserve.

METHOD (B)
The pH may be controlled with carbon dioxide infusion. the strength of the reserve and the quantity of carbon dioxide infused will determine the pH. For pH to read without carbon dioxide interference, carbon dioxide has to be in equilibrium with the atmosphere. Carbonate hardness is the basis of the pH, but this pH value can be over-ridden by increasing the carbon dioxide levels causing a lower pH.

Published by AQUASONIC