Alkalinity Supplement Calculator



Stable water chemistry is key to having a beautiful, trouble-free marine and reef aquarium. Marine fish, SPS and LPS corals and other invertebrates require stable aquatic conditions to remain healthy in the captive aquarium environment. Fluctuations due to natural processes in the aquarium are often slow and gradual but can happen quickly due to the relatively small volume of water and heavy livestock load often seen in reef aquariums.

It can be difficult to impossible to duplicate the stability of the natural reef in the home reef tank. But through careful and deliberate testing and dosing of essential additives we can come very close.

Alkalinity, also known as KH (carbonate hardness), is a key water quality parameter important for keeping fish as well as reef invertebrates. Alkalinity is a chemical measurement of the water’s ability to neutralize acids. This is important because the biological and chemical processes involved in eliminating fish and invertebrates wastes produce acids and reduce the alkalinity level in the water. Alkalinity is also a measure of a water’s buffering capacity. pH buffering capacity is important because natural biological and chemical processes in an aquarium will work to raise or lower pH levels. Alkalinity provides the buffer capacity to resist swings in pH.

In the marine aquarium, alkalinity is provided primarily by bicarbonate (HCO3-) and carbonate (CO32-) ions. Over time, alkalinity will be “used up” as it fights to keep the pH stable. Once this happens, the pH fluctuations will be greater, and the aquarium’s pH will shift to an undesirable range.

Alkalinity is also of utmost importance for keeping LPS and SPS corals. The zooxanthellae algae living inside the coral tissue provides essential energy for the coral. The algae use light, nutrients and carbon to drive photosynthesis. Photosynthesis provides the corals with glucose, glycerol, and amino acids which the coral use as energy to build new tissue and coral skeleton material. Zooxanthellae algae, like other plants, need carbon to thrive. They’re able to use carbon dioxide (CO2) from the aquarium water but it’s not enough to keep the photosynthesis operating at a normal rate. The corals bring bicarbonate (alkalinity) to the zooxanthellae algae as a carbon source. Experiments have demonstrated that low alkalinity levels inhibit photosynthesis and reduce coral growth. Likewise, maintaining alkalinity levels can increase LPS and SPS coral growth rates.

Dosing of alkalinity supplements is necessary to maintain optimal levels for pH stabilization and coral growth. This requires testing the water with an alkalinity test kit to find the baseline KH level. Then, the correct dose of alkalinity supplement needs to be added to bring the KH up to the desired level. But how much to add? To add to the confusion, alkalinity can be measured in three different units: meq/l, dKH and ppm (mg/l). While any unit can be used, it can be confusing to if your test kit uses one unit of measure and the alkalinity additive uses a different unit in the dosing recommendations.

We’ve solved this problem with our Alkalinity Dosing Calculator. Just plug in the aquarium volume, current alkalinity level and the desired level. But there’s more! We’ve added the most popular alkalinity-boosting products to the calculator. This means you’ll get the right dosage rate, based on the product you’re using. What could be easier than that!