The introduction of corals is arguably one of the most exciting parts of setting up a marine aquarium. However, the process can be daunting, especially for newcomers to the hobby. Unlike the other inhabitants of a marine aquarium, corals are only able to move over a very long period of time. Therefore, corals are entirely dependent upon the hobbyist to provide them with the conditions needed to thrive.
In this piece I shall offer a straightforward (and very simple), overview of the basic conditions that corals require in captivity and how we maintain them and then I will look at how to add some of what I would regard as the most straightforward of corals for the beginner.
The key to maintaining healthy corals over the long term, whether delicate Acroporids or more hardy zoanthids, is stability. The more stable you as an aquarist can maintain the chemical composition and other environmental factors in your captive reef the less any inhabitant in the aquarium will have to expend energy to adapt to change. The closer those parameters are to those encountered in the coral’s natural habitat, the healthier they will be and the more likely they are to survive. A healthy coral is characterised by nice polyp extension, colour and growth.
Most Important Water Parameters to Monitor
Salinity, Alkalinity, Calcium and Magnesium are the most fundamental water parameters to monitor and maintain. Salinity should be maintained in the region of 1.024 to 1.027 (35 parts per thousand or thereabouts). Salinity can be allowed to vary, albeit at a very slow rate (over the course of weeks). Any variations to salinity should be corrected slowly. Rapid changes in water parameters can cause excess stress for the inhabitants of the marine aquarium. Salinity does not change significantly in coral reefs and therefore, these conditions should be replicated as much as possible.
Calcium needs to be maintained at around 400-450ppm in the aquarium. It is the main constituent in the formation of coral skeletons (calcium carbonate as aragonite), and the shells of creatures such as Tridacnid clams. It can be maintained using over the counter solutions, kalkwasser additions or more commonly via a dosing regimen such as Balling Light or a calcium reactor. Maintaining calcium is not difficult, but it should not be varied by more than 20ppm a day and as the amount of coral in a tank increases the amount of calcium added will need to be increased.
Being a co-precipitate in skeleton-genesis, magnesium is important in coral growth and in many life processes, though the amount of magnesium locked up in coral or coralline algal tissue is far less (<2%) when compared to calcium. Once again magnesium can be added via liquid solutions, but is best added via a dosing regimen or via a calcium reactor. The benefit of adding it with a calcium reactor is that as the media dissolves the ratio of calcium to magnesium is maintained correctly. Try to maintain magnesium at around 1250-1350ppm in your tank.
The alkalinity of our systems is a complex matter that is influenced by many factors. Although there is ample information out there in regards to alkalinity, the practical application is that additions to adjust one parameter can effect change in another.
Test kits for alkalinity are easy to use and reliable, a figure of between 7-and 12 dKh is considered ideal. Many aquarists will maintain their alkalinity at the higher end of this scale to provide an increased amount of buffering capacity which is useful in a volume of water vastly smaller than the ocean.
The easiest way of ensuring that alkalinity, calcium and magnesium are in the correct balance is the use of a good quality calcium reactor, which may be a hassle to set up initially, but when running correctly will deliver the bulk of these substances in the correct ratios by dissolving the same substances the corals are using to build their skeletons, i.e. old coral skeletons. Water chemistry is a complex subject, and the beginner needs to understand that there is a lot more going on than may at first be apparent. However, with small changes to a systems water quality and regular testing the aquarist will develop a sense of how each adjustment varies the conditions within the aquarium.
With the advent of modern technology, maintaining water temperature is relatively simple. Depending on where you live in the world, will depend on what sort of equipment you need. If you live in a warmer climate, a chiller as well as a heater may be necessary. Temperature fluctuations should be non-existent, therefore, if there is one piece of equipment you should NEVER skip it is the chiller. I have heard countless stories of hobbyist losing all their livestock over the period of several hours during a ‘warmer than normal’ day.
Water flow preferences differ between corals and flow-rates presents an enormous subject for discussion. Bear in mind that on the majority of the world’s reefs, water movements can be considerable. This isn’t of course the same for every coral, and those that are found in deeper waters may not be best suited to high flow areas. Consider the differences between a torch coral and a staghorn Acropora (See: Keeping Acropora and Other SPS Corals). The former will be ripped to shreds by vigorous water movement, whereas the latter will thrive on it. The key here is to talk to the staff at your LFS and do your research.
In terms of lighting, most commercially available lighting advertised as suitable for keeping corals will be able to do so, the main risks for the first time coral keeper is fitting high intensity lighting to a tank and ‘blasting’ corals and inverts with strong lighting that they are not accustomed to. Even species and genera that are tolerant of very strong lighting in the wild may require time to adjust to lighting in the captive tank, especially with some of the lighting units using LED technology that generate ‘hotspots’ directly under the arrays. Again do some research and when you introduce your corals to your tank consider placing them on the substrate away from ‘hotpots’ and raise them to their final position in the tank over a period of a week or two. I would rather a coral lose colour and require extra lighting to be added or it to be moved rather than bleach it from too intense a light source.
Again, the best advice for the newcomer to the hobby is to chat to other aquarists and seek out knowledgeable staff at stores. Bear in mind that if someone in the store won’t sell you a coral, they are perhaps doing you a favour and you should not be offended.
Quarantine is an essential process for any hobbyist to undergo. Aquarists with extensive collections of corals will be very wary of adding corals to their systems without quarantining them first in the hope of identifying any disease or pest organisms before the infection becomes manifest in the main aquarium. It is likely that the newcomer won’t yet have set up an isolated system for such a purpose. If this is the case consider one of the many coral dips available which can be used to treat corals to remove potential pests like coal eating flatworms.