Calcium reactors (continued)
Disadvantages: Like all methods, calcium reactors are not without some drawbacks.
- These units are relatively expensive initially. In addition to the reactor itself, a properly set up unit will also require a tank for carbon dioxide, a regulator and needle valve, and a means for assessing pH.
- Care must be taken in the selection of the media. Some media may contain a lot of phosphate, so that as the media dissolves, phosphate is released, as well. Fortunately, in the last year, phosphate-free media such as Korallith is now available.
- The amount of carbon dioxide being introduced needs to be closely monitored so that excessive carbon dioxide is not leaked into the tank. If this occurs, a constantly low pH reading will result. However, when a properly functioning needle valve and bubble counter are being used in combination with a pH monitor, there usually is no problem.
- Calcium reactors may increase alkalinity to excessively high levels if they are not monitored closely. This can be controlled by the addition of calcium chloride from time to time, or by adjusting the flow rate and the rate of carbon dioxide introduced.
I have now been using a reactor for over five years on one of my tanks, and other than getting it adjusted initially, it has produced very few problems. While there are considerable start-up costs associated with implementing such a system, a calcium reactor may prove to be a wise long-term investment by saving you time, money, and frustration while maximizing your coral growth. For more information see: Calcium Reactors.
Calcium reactor and kalkwasser combination
One of the latest advances is to use both a calcium reactor and a kalkwasser reactoron a tank that consumes a large amount of calcium. This combination maintains both calcium and alkalinity levels even better than using a single reactor and also results in a reduction in phosphate levels and stable pH. In my opinion, this may be the optimum way of maintaining calcium levels in a large SPS tank. However, it should be noted, as with most aspects of reefkeeping, there are always numerous ways to achieve the desired result, so the experimentation within the hobby will continue. This is how the hobby has progressed to the point it is at now, where SPS corals are commonplace, and their growth rates in some tanks can exceed the rates seen in the wild. Understanding and implementing proper calcium supplementation and alkalinity may seem difficult at first, however, over time, with proper testing and patience, keeping these compounds at their proper levels is actually quite simple.
Testing
Regardless of the system used, while supplementing calcium, there is a need to frequently test the tank's water for the calcium level. Once a good method for supplementing calcium is chosen, we often quit testing thinking that we are done. Calcium supplementation is not a static process; as coral colonies, both soft and stony, grow, and as coralline algae spreads, these organisms all take up more and more calcium. As a result, the supplementation of calcium generally needs to be increased over time. If testing is not done regularly, it is very easy for the levels to drop precipitously, owing to this increase in demand. For this reason, it is my experience that calcium levels should be assessed every two weeks or so, or even better, once per week. To do this, several reliable test kits are available. At the same time, alkalinity should also be measured, as there is a relationship between calcium levels and alkalinity that should be monitored. These same companies also make very good alkalinity/KH test kits. The reason that both of these measures need to be monitored is that if the calcium levels get high (over 500ppm), there is a tendency for the alkalinity to drop. Conversely, if alkalinity levels get too high, calcium levels will tend to fall, as calcium precipitates out in the form of insoluble calcium carbonate. Therefore, when calcium is measured, the level should be between 400ppm and 450ppm, while the alkalinity level should be between 2.5-3.5 meq/L (milliequivalents per liter) or 7-10 dKH (carbonate hardness as measured in degrees).
