Kalkwasser, Medical Grade Calcium Hydroxide, Balanced Method to Maintain Calcium and Alkalinity in a Reef Tank

Kalkwasser is one of the easiest (and most cost effective) methods to maintain calcium and alkalinity in a reef tank. There are several ways to dose Kalkwasser, including the methods below. Whichever method is used, you should carefully monitor your tank’s pH, calcium and alkalinity levels and adjust the amount of kalkwasser used based on changes.

MIXING SOLUTION
Add kalkwasser into RO/DI Water to create your solution based on your established demand. For lower kalkwasser usage rates, or if you wish to add slowly and adjust, you can start at the lowest level of ½ teaspoon per gallon of water, or adjust upward by ½
teaspoon increments, up to a maximum of 2 teaspoons of kalkwasser per gallon of RO/DI water for a fully saturated solution. Add the kalkwasser to RO/DI water and stir lightly until fully dissolved, allowing the mixture to settle for 20-30 minutes.

DOSING WITH AN AUTO TOP-OFF (ATO) RESERVOIR

Fill your clean top-off reservoir with RO/DI water. Create your kalkwasser solution in the water based on the mixing amounts suggested above. Turn on your ATO and add water to replace your natural evaporation. Monitor your tank’s pH andcarbonate alkalinity levels as you replace the tank water with the ATO reservoir for the first week. You should adjust the rate of addition to your tank so as to maintain a stable pH (ideally keep between 8.3 - 8.4, and no higher than 8.5), and ensure pH does not spike by more than 0.2 as you dose. If your alkalinity is rising, reduce your concentration; if it’s falling, increase slightly (up to 2 tsp per gallon max).

DOSING PUMP

Create your kalkwasser solution based on the mixing amounts suggested above - anywhere between ½ teaspoon to 2 teaspoons of kalkwasser per gallon of RO/DI water. Add this solution to your dosing container, and connect and program your dosing pump to deliver the solution slowly (especially at night, to balance your pH).You can start with a dosing rate of 0.1–0.2% of your system volume per day, then test and adjust every 2–3 days. Example: to dose a 100 gallon tank, you can start with 100–200 mL per day, and test alkalinity daily and adjust upward until your dKH stabilizes at your target (e.g., 8.0 – 8.5).

KALKWASSER REACTOR

Refer to your reactor’s instructions for dosing kalkwasser.