CHEMISTRY AND THE AQUARIUM by RANDY HOLMES-FARLEY
Solving Calcium Problems
For many reefkeepers, correcting undesirable calcium1 and alkalinity2 values can be among the most vexing of the chemical problems encountered in maintaining a reef tank. Most reefkeepers know that if these parameters are not maintained appropriately, corals and other organisms may have difficulty3 in depositing calcium carbonate skeletons. Understanding how to solve such problems, however, proves more elusive. Unfortunately, it is often not as simple as adding more of whatever is depleted.
Here, for example, is a real question that typifies the problem:
I'm having problems raising my calcium levels above 200 ppm. I have been using kalk for about two weeks for all top off water, about 3/4 gal a day. The level has never gone above 250 ppm and drops back to under 200 ppm. I bought some Turbo Calcium and tried it as the product label recommended but am having no real success. I have never used Turbo Calcium before and was wondering how much of it I could dose safe. I only have 2 mushrooms and 2 damsels. Any advice?
Unfortunately, calcium and alkalinity are linked4,5 in many ways in reef tanks, and these links can lead to serious problems if they are not fully understood. If, for example, you add too much of a calcium supplement, you will drive down alkalinity as you get precipitation of calcium carbonate in the tank. Likewise, adding too much of an alkalinity supplement can result in reduction of calcium. Consequently, trying to correct one problem can cause another. Moreover, if you try to correct a calcium or alkalinity “problem†with the wrong type of additive, you might accomplish nothing more than creating limestone in your tank.
This article will clarify the different types of calcium and alkalinity problems encountered in typical reef tanks, and will describe in detail how to “solve†each of them. In reading through the article, you may feel that I am making it unduly complicated. Remember, however, that this article describes how to solve many different problems, while any given tank can only have one of them, so only a small section will apply.
Unlike most of my articles, this one is not written to provide a deep understanding of the science behind calcium and alkalinity in reef tanks. Those topics have been dealt with in several of my prior articles. This one reads more like a recipe. Nevertheless, this is the procedure that I go through (in my mind) when giving advice about correcting calcium and alkalinity additions, and there really is no shortcut that will ensure success (and plenty that ensure failure).
At the end of the article, I’ll also emphasize the best way to avoid these problems: using balanced calcium and alkalinity additions. I believe that using such additives would eliminate the majority of problems that people have with calcium and alkalinity, and I very strongly recommend their use.
One caution: many people get faulty readings from aquarium test kits. Some of these problems are the fault of the kit, and some the fault of the user. Regardless, if an aquarist were to “correct†a problem that was really only due to a faulty measurement, then the tank may go from fine to disaster. So please, before making any big corrections to water chemistry, confirm the reading with a different kit, preferably a different brand. This caution should especially apply if the measurement does not seem to make sense based on what you have previously added to the tank.