Alkalinity is one of the most critical parameters in a reef tank. Unstable levels will cause an aquarium’s pH to fluctuate, which can cause damage or even death to corals, fish and other livestock.
Alkalinity is also a critical component in forming coral skeletons, and low levels will significantly reduce coral growth rates. Therefore, regular replenishment (typically on a daily basis) is generally required to maintain stable levels of alkalinity.
What is Alkalinity?
Alkalinity is the ability of the water to buffer acids and maintain a healthy pH.
Why is it Important?
Proper levels of alkalinity keep pH stable, prevent coral tissue loss and prevent the bleaching of corals. It also provides the carbonate and bicarbonate that corals need to build their skeletons.
What is the Optimal Range?
Reef Aquariums: 8-12 dKH
Note: if levels are too low or high, please adjust them slowly.
Tools for Measuring Alkalinity
Hand-held Tester:
A hand-held tester (aka a colorimeter) calculates alkalinity based upon the amount of light passing through a liquid sample.
Although hand-held testers are usually more expensive, they are also typically easier to use and more accurate than standard test kits.
Standard Test Kit:
Standard test kits are an inexpensive and readily available method for measuring alkalinity levels.
However, the testing process can also be tedious and inconsistent. While they’re typically less expensive than a hand-held tester, standard test kits do not always provide the most accurate results.
How to Maintain Alkalinity Levels
The demand for alkalinity will vary significantly depending upon the type of corals, the number of corals as well as the size of corals in a tank. For example, tanks with more LPS and SPS corals have a significantly higher demand for alkalinity than tanks with primarily soft corals. For new tanks without hard corals, a regular weekly water change may be sufficient. However, as a tank matures with an increased number and size of corals, frequent dosing is usually needed.
How to Adjust the Daily Dosage of Alkalinity:
Consistent test results are critical for calculating a tank’s daily alkalinity dosage. As such, we recommend testing your tank’s levels using a hand-held colorimeter over a standard test kit. It is also crucial to measure the tank’s levels at the same time each day as the consumption of alkalinity will vary throughout the day and night.
If your levels change by 0.3 or more from one day to the next, adjust the dosage immediately. If your levels change by 0.2 or less, do not change the dosage. Continue testing daily until KH values do not fluctuate by 0.3 or more and do not exhibit an upward or downward trend for three straight days. Check levels at least once a week after that to ensure the dosage does not need to be adjusted and that the range is stable.
The Relationship Between Calcium, Alkalinity and Magnesium + How to Prevent Calcium Carbonate from Precipitating Out of the Water
Corals need alkalinity and calcium to build their skeletons and grow. However, the coral can only use them if they are independent ions “floating” around in the water. If these combine in the water column to form calcium carbonate, they will precipitate out of solution and be unusable to the corals in the tank. Proper magnesium levels between 1250 – 1350 ppm prevent the alkalinity (carbonate and bicarbonate) and calcium from combining.
And there it is! Alkalinity is arguably one of the most critical and essential elements in a reef tank. If levels run too low, corals can rapidly lose their tissue and pH levels can fluctuate. If levels are too high, the tips of a coral can “burn,” causing them to lose tissue. Keeping this parameter stable in a reef tank is essential in healthy coral growth and coloration.
Have a question? Feel free to contact us for more details regarding how to maintain your tank. If you are in the market for new tank equipment or supplies, please visit our website here: ATI North America.