Marine Aquarium Lighting Is Really Important

A well set up and stocked mature marine aquarium is beautiful, even to those who are not interested in having one. Anyone passing by one of these aquariums, be it private or public, will stop and gaze.

Setting up a marine aquarium takes time and patience but when done it is well worth it. A lot of attention is paid to the equipment and quite rightly so. The livestock depend on the correct choices so that the habitat is suitable and healthy. Lighting has long been used in the home and commercially to enhance for different effects. Spotlights are an obvious example, another is colour designed to attract attention or maximise the feeling of comfort. Colour is also used in the marine aquarium but in this case it has to be more specific particularly in a reef system. On the natural reef many corals and other lifeforms are collected from between 15 and 30 feet (not precisely of course!). Because of this depth they have become, over a very long time, accustomed to the light in this area. At the surface of the sea all the colours of sunlight are present. The sea absorbs light as it passes down into greater depth. The first to disappear are red, orange, yellow, indigo and violet. The deeper into the sea the more blue it becomes. At the levels mentioned  the ‘red end’ of light has gone and therefore corals have evolved to make use of that remaining, particularly blue. This is not an overall rule as there are lifeforms that are close to the surface and can make use of other colours, but for the marine aquarist blue is important.

Why should blue be important? Within the flesh of most corals kept by aquarists are tiny algae cells, millions in a single coral. These algae cells, called zooxanthellae, help the coral to feed and dispose of waste. They are very important to the coral and if something goes wrong and the coral ejects them, called bleaching, there is trouble. We’ve heard of coral bleaching on the wild reefs, a cause for concern. So the lighting that we provide is very important. (There are more causes for coral bleaching than lighting problems.)

Lighting types can be identified by means of the Kelvin scale, simply shown as a K after a number. For example, at the seawater surface natural sunlight is rated as 5,500K, the number representing a very warm white light. 20,000K represents a cold looking blue light and represents deep water areas.

With a fish only system the lighting is not of such great importance as there aren’t any corals present. The fish need to see and the aquarist needs to see the fish, that’s just about it. However, if warm white tubes were to be used there is a danger that unwelcome algae could be encouraged so this is not a good idea. It is suggested that two tubes are used with reflectors, one white and one blue as described for a reef system. This will also enhance some fish colours as a bonus.

The reef system is more demanding with light. Again, it is suggested that two colours are used, one being white and the other blue. As many tubes as can be fitted with reflectors should be used. The whites and blues should be in equal numbers and fitted alternately, or if it is an odd number the extra should be a white. It can’t be any white or any blue though, we need to have specific light output. With fluorescent tubes these should be what is commonly called ‘marine white’, that is tubes that are 10,000K or close. The blue tubes are again commonly called ‘marine blue’ and are often sold quoting ‘400 -480nm’ (nanometers) and could also state that the output peaks at 420nm. Why? This is because the range and peak quoted represent the area required in particular by the corals for their tenants, the zooxanthellae.

This all sounds rather technical but for the aquarist it isn’t a problem. Fluorescent tubes are often sold declaring their intended use hence ‘marine white’ and ‘marine blue’. There isn’t a requirement to put on a white coat and look scientific. The manufacturers have designed their lights for specific use and are usually easy to select.

The blue tubes have another advantage and this is that they could make some corals look wonderful because they fluoresce. This is caused by the UV output from the tube impacting the coral and is not a problem. The photo at the beginning shows my aquarium with all fluorescent lights on. The photo above shows the aquarium with blue lights only. The following photo shows the lighting array, three whites and two blues. The aquarium is 24″ deep and contains soft corals.

There are of course lighting systems other than fluorescent tubes. Though more expensive the LED array is the most modern concept. Used a lot on reef systems but possibly declining by now because of running costs is the metal halide system. These mentioned systems have not been covered here as it is more advanced and fluorescent tubes are perfectly suitable for ‘standard’ aquarists. Remember though to have regard to the depth of the aquarium, that is the depth the light needs to penetrate.

Having white and blue lights has the advantage that the aquarist can arrange a ‘dawn/dusk’ sequence using electric timers. It is bad practice to plunge the aquarium into darkness or instantly expose it to bright light. Have the blue lights come on first (dawn) and 15 minutes later the white lights. At the end of the day have the white lights go off first and 15 minutes later the blue lights. Though not matching the natural events it works well. The lights should run between 8 to 12 hours a day. Try 10 hours, then reduce or increase by half an hour over an extended period if wanted (nothing should be rushed).

As time passes there is a requirement to change fluorescent tubes. This is because as they age the light output reduces and the spectrum can shift. If tubes are not changed then there could eventually be a detrimental impact on the zooxanthellae and therefore the health of the corals. The manufacturer should suggest the frequency of renewal. Fluorescents should be changed no later than one year old, I change mine every nine months. My soft coral reef has been running for over 10 years now with the same type of lighting system and has flourished. The fluorescent tubes are T8’s, not the later T5’s. Sometimes the corals are a bit too vigorous and this leads to some ‘fragging’ (pruning of corals where the cut off pieces are grown into new corals). In the first two photos a cut can be seen on the bottom left large coral.

The number one on the list of importance for a marine aquarium, fish only or reef, is seawater quality. With a reef system, a very close second is lighting. Pay attention to both and the aquarium should be truly beautiful.