There is a variety of equipment to assist in the maintenance of a marine aquarium. Some are essential such as the heater/thermostat, others are supportive for example the auto top-up system. The calcium reactor is often supportive, but in some circumstances it can be argued that it is essential.
First of all, what is a calcium reactor? This device is a means of getting calcium into the seawater. This is achieved by slowly moving the seawater through a calcium rich media in an acidic environment. The device is attached to two inputs, first seawater and second carbon dioxide. The seawater is as said fed into a media area where the gas is present. The gas is injected under careful control, usually a bubble count. The acidic environment created causes the media to dissolve and the seawater carries calcium into the aquarium. The flow rate is slow, counted in drips per second or similar.
The amount of calcium demand is the key to the usefulness and effectiveness of using a calcium reactor. There is a need to measure the calcium in the aquarium, so the only way to know is to test. Testing will let the aquarist know what calcium presence there is, but what needs to be replaced for that which is used? The answer lies in doing an ongoing weekly test as in this way the calcium demand of the aquarium can be ascertained. When the amount at the end of the period is subtracted from the amount at the beginning an indication of the demand is obtained.
If the aquarist is running a fish only aquarium then a calcium reactor is not required. If the system is a reef then the aquarium size has an effect.
A small aquarium will house a smaller reef which in turn will support less corals. So the calcium demand is going to be lower. It is more than likely that a soft coral reef will need little or even no supplementation as these corals have a low demand. A hard coral reef such as SPS will have a higher demand.
A large aquarium will obviously usually house a large reef with many more corals. In this case, though soft corals have a low demand for calcium, because of the number the need is going to be greater and supplementation may well be required. It is generally safe to state that a large reef with many hard corals such as SPS will need supplementation.
Having determined the amount of calcium loss over a week, the aquarist can now determine the best way of replacing it. There are two main ways, one is to use commercially produced supplements that are available in liquid or powder form or a calcium reactor. The choice will be determined by cost and convenience.
On the small reef, the soft coral one, the demand as said will be low. In this case it is likely to be financially sensible to use a commercially produced supplement. With the low demand the supplement is going to last for many uses and therefore will not be an excessively expensive option. If it is a hard coral reef the demand will be higher and the aquarist will need to consider how long a supplement package will last and the cost involved, and then make a decision about using a reactor.
The large reef if a soft coral one may still have a calcium demand that can be sensibly met by a purchased supplement. The hard coral reef however is going to need a much larger amount and so only perhaps three or four doses will be available for each commercial supplement purchase. This is going to prove expensive as time progresses.
Having done the tests the aquarist is aware of the calcium demand per week, so a decision can be made. For the large reef, certainly the hard coral type, it will be better to employ a calcium reactor. Even though routine seawater changes are done the calcium shortfall will not be made up and package supplementation will be expensive and impractical. For the smaller aquarium the aquarist may decide to employ a calcium reactor for the hard coral reef, even though package supplementation is an option, as the reactor is convenient and once purchased less expensive to use.
The lowest guideline for an SPS reef calcium level is 400 parts per million (ppm), but it is usual to maintain a level of around 420 to 450ppm. A little rise and fall in the level seems not to be a problem. This rise and fall will occur when weekly supplementation is employed using a commercial product, but is less or removed with the use of a reactor as the device is applied continually or more regularly.
It is important when using a commercial supplement or a reactor to follow the manufacturer’s instructions. The commercial supplement is straightforward but some initial additional attention to testing is needed with the reactor. How fast is the drip rate? The faster it is the more calcium is entering the aquarium. Adjustment should permit the calcium requirement to be met. Attention must also be given to the amount of gas entering the media chamber, this is usually indicated by a bubble rate.
Even though testing to establish the calcium demand has been done in the early weeks, the final demand cannot be discovered until the reef is fully stocked with corals. The ongoing demand will also vary to an extent. It is good husbandry to continue testing for the calcium level so that changes can be catered for.
Maintaining an acceptable calcium level will prove to be very worthwhile, the corals particularly hard types will benefit and also small reef life such as shrimps and snails.