Kalkwasser: The Easiest Way to Maintain Ca, Alk & pH

A lot of reefers choose kalkwasser because it’s cheaper and easier than dosing two part, and its WAY cheaper and easier than a calcium reactor. One disadvantage is that because it needs to be dissolved in a large volume of water, so it’s not as scalable. Since you can’t add more water to the tank than evaporates, so you’re somewhat limited to how much you can add in a day. Generally though, you can add enough kalkwasser solution to satisfy the demand of any LPS tank, most mixed reef tanks, and even some SPS tanks! Corals pull calcium and carbonate ions out of surrounding water to build this structure. If we want them to grow, stay healthy and maintain coloration we need to replenish the calcium and carbonate the corals removed. Kalkwasser can replenish both elements in one simple solution. Kalkwasser is a calcium hydroxide powder that, when dissolved in water, will separate (ionize) into calcium and hydroxide ions. Obviously, the calcium provides calcium to the tank. The hydroxide reacts with the carbon dioxide in the water to create carbonate and bicarbonate to provide the alkalinity. This is how kalkwasser replaces both calcium and carbonate alkalinity. It also reduces carbon dioxide which raises the pH in the tank. This is beneficial because, as most reefers believe, corals calcify and grow faster and pH’s closer to 8.3, which is hard to maintain without additives like kalk. There are a few ways to add kalkwasser to the tank, but all of them add the kalkwasser solution very slowly. Usually over the course of many hours or even the entire day typically with a slow drip or small, infrequent spurts. Slow is key as kalkwasser raises the pH of your tank significantly, so you can only add small amounts in a single dose. The easiest long-term solution is likely to mix kalkwasser into the freshwater holding container for your auto top off. Another way would be an inexpensive kalkwasser dripper, which is a bit more manual but cheap and achieves the same goals. Let’s start with what I think is the best solution; adding kalkwasser to the top off. This is a great solution for newer or mid-level reefers that want a super easy way to maintain calcium, alkalinity and pH in addition to solving your tanks evaporation needs. It’s as simple as adding the appropriate amount of kalkwasser powder to your freshwater storage container. How much kalk you add will be a combination of how much water generally evaporates from your tank, and how many corals are in your tank. 2 teaspoons is the maximum amount of kalk that can be dissolved per gallon of water. If your tank evaporates very little water you may want to make the solution more potent with the full 2 teaspoons per gallon of freshwater. If you evaporate multiple gallons a day you might want to try 1/2 a teaspoon first and work your way up. Once you’ve determined the amount of kalkwasser you need to add to your container, it’s time to mix. The water will turn a milky white color after mixing, commonly called a kalk slurry. We definitely do not want to dose this directly to the tank. Allow it to settle out for a few hours and the water will become crystal clear with white sediment at the bottom, which is a mix of undissolved kalk and some precipitates. You don’t want to dose the sediment directly to the tank either, so you can suspend your top off pump a few inches off the bottom or place it in a container within your auto top off container to prevent it from sucking water directly from the bottom. Another dosing option would be a dripper. If you’re into DIY, this is a great option because you can basically build one out of any container. You’ll just need some tube and a valve of some sort. Checkout Reef Keeping Magazine for some instructions. To use the dripper, you’ll fill it with freshwater, add kalkwasser powder and stir and let sit for a few hours. Again, you’ll see some precipitate or undissolved kalk at the bottom, so your feed straw should not go all the way to the bottom of the dripper. Once it’s settled, you’ll just need to create a siphon and drip the solution into your tank or sump. Remember; slow is key. Regardless of what solution you decide on, you should start testing calcium and alkalinity daily in the beginning to ensure you have the right potency. You could also pick up at pH test kit, and test before and after dosing so you can get an idea of the kalk’s effect on pH. If you have budget for it, a monitor like the PinPoint or controller like a ReefKeeper or Apex is even better! A few last pointers on Kalkwasser: once it’s mixed, don’t mix it again. You want to limit the amount of carbon dioxide the kalk solution interacts with since it depletes the strength of the solution. Make sure you have a tight fitting lid on your containers for the same reason. Connect with us on Facebook: Check out our pics on Instagram: