What Is It?
Calcium hydroxide solution, or Kalkwasser (also known as "lime water," the literal German translation of the word), is a form of calcium supplement that many avid aquarists use to maintain their fish tank's calcium levels, especially in refugium or reef aquarium systems.
This is very important, because when you change the water in an aquarium tank, the salt (sodium) levels remain constant, but other nutrients, including calcium, are lost as old, more established and nitrified water is replaced with clean, fresh, and purified water.
What Does It Do?
For starters, the calcium in Kalkwasser helps begin to make up for the high levels of evaporation that occurs, especially in more advanced fish tanks. Aquariums such as those with strong water pumps and skimmers are particularly in need of this type of calcium supplementation. Although calcium is a much-needed supplement for almost all aquatic life in your tank, this is especially true for refugiums (reef ecosystems), which lose calcium at alarming rates.
Kalkwasser also keeps the pH level stable and elevated, much closer to the recommended levels of just above 8 (a level between 8.2 and 8.4 is often recommended). This also means that the supplement will inhibit the growth of harmful and pesky micro-algae, while encouraging the growth of beneficial pink and purple coralline algae.
How Do I Use It?
Kalkwasser may be purchased at any pet or aquarium supply store. However, when you bring it home, be sure to follow the instructions. It is a strong, concentrated liquid, which must be carefully mixed with water before introducing it into your aquarium. It is recommended that you always use purified water when mixing your Kalkwasser, as tap water can introduce a wide variety of other chemicals and impurities that could completely ruin the positive effect you're trying to achieve with the lime water in the first place.
The Kalkwasser supplement also significantly increases pH levels, so it's best to add it to the tank either very early in the morning or late at night, when the pH levels in the tank are naturally at their lowest.
In terms of how much to add to your tank, it's important for you to have water-testing kits that will help you determine the calcium, alkaline, and pH levels in your tank. What you're striving for, when adding Kalkwasser, is for your tank to reach and maintain a calcium level of 400 mg. per liter. You'll also need to vary the amounts you add, depending on how often you introduce new reef coral or organisms to your refugium or aquarium.
Kalkwasser is an extremely beneficial supplement to any aquarium, but is certainly most advantageous for a reef ecosystem. Most experts agree that adding it will make a significant difference in the quality of your tank. Just be sure that when you buy your Kalkwasser supplement, you read the instructions carefully before introducing it into your particular system, as its concentration can make it difficult to manage in terms of achieving optimum levels.
