Water quality (in which I include water movement) is top of the list in importance when it comes to keeping a saltwater aquarium. Closely following water quality is aquarium lighting, as much life on the reef depends on it.
The lighting used for a reef aquarium is more intense than on any other type. The reason for this is that we are trying to simulate the sun as far as humanly possible. Reef aquarium lighting is normally more towards the blue end of the colour spectrum as we are trying to produce the lighting colours present at between 10m and 30m in water depth.
Colours are lost the greater the water depth is, the first loss is red. The reason we choose colours present at the depth given is that is the depth where the majority of corals are obtained.
The provision of lighting for a marine reef aquarium needs careful consideration. The depth of the aquarium, distance of the lights from the water, and the type of animals you wish to keep are questions you need to ask yourself.
In the aquarium corals receive energy from the light which is provided for them. The remainder of the energy required is from the corals themselves actively feeding. I will produce a post in the future which will cover various ways to feed your corals.
In the marine reef aquarium the aquarists has a responsibility to supply the light the animals would receive in the wild as far as possible. Obviously we cannot equal the sun itself, particularly its intensity, however we can produce the spectrum of light essentially required.
In the wild the light provision is simple. In basic terms light is provided for around 12 hours a day and a night period of around 12 hours. The light provided by the sun is very intense even when there is cloud cover. The amount of lighting wattage we would need to provide the aquarium to even come close to this sun power would be enormous. In terms of cost and physically fitting the lights it is clearly of no use to an aquarist.
Some people wonder why they purchase a really colourful coral, take it home and over time it loses it colour or its colour dulls. The reason for this is they are used to a certain amount of light, both intensity and colour spectrum. A marine reef aquarist purchases the coral, takes it home and places it in the aquarium and both the light intensity and the spectrum are different to what it is used to or requires. If the lighting is not strong enough or too strong, or of the incorrect spectrum then the coral could lose its colour.
Can’t win! Well, it’s not that bad in reality.
Another thing we could consider producing are ripples on the water surface. There are some aquarists who do not see this as relevant. The way I see it is that it is like this in the wild so we should carefully consider producing these in the aquarium. Ripples on the water surface create a shimmering effect, and there are lots of discussions going on at present as to whether this has any importance to corals. In a reef aquarium, water movement is such that ripples are likely to be produced without any additional effort.
Another aspect is cloud cover – again in the wild the skies are not clear all day long – there are times when there are clouds in the sky. This is something again which you may want to consider when investiating your lighting options. There are lighting models available nowadays which attempt to simulate this.
Another type of lighting which you could consider applying is artificial moonlight. There are various devices available for this. Also there are various theories as to why applying moonlight is of benefit – one of which is coral spawning.
When we consider the power of our lighting, we are thinking in terms of watts. A halide bulb, for example, could be 150 watts, 250 watts, 400 watts etc. As the wattage increases the light is generally more powerful and intense.
Another important point which needs to be discussed is the lighting colour spectrum and the effect which water depth has upon it. While the importance of intensity is well known the colour spectrum is something which must not be ignored.
Light is a combination of different wave lengths which range from the invisible ultra violet, to the blues and yellows etc, on to the infra red light at the other end of the spectrum which again is invisible. These different wave lengths (colours) are rated in Kelvin. It is often referred to as the colour temperature.
The aquarist needs to apply the correct colour temperatures, or Kelvin rating, in the lighting as most corals require this to continue their life functions.
This is where we move on to the next step. Why do corals need lighting, and why is the colour of the light important?
The reason is the zooxanthellae, otherwise known as symbiotic algae, which live within many corals. The zooxanthellae use the light as a source of energy. The coral receives sugars which are the ‘paymentt’ from the zooxanthellae. The zooxanthellae primarily use the blue end of the spectrum. When light hits the water surface red light is the first to be filtered out and so on until, at the depths where many corals exist, generally speaking blue is prevalent.
It must be pointed out that the foregoing is a very simplified version of a complicated subject.
Lucky for the aquarist that light colours are lost as water depth increases. As said, we cannot generate the power of the sun. We can generate enough power for our needs, and the colours of light required by our corals.
When discussing marine lighting, “blue (actinic)” often crops up. This is light, mainly generated by fluorescent tubes, which is used both on a full fluorescent lighting system, and also on a halide system. This blue light is used for the reasons already discussed.
So there we go, in vary basic terms the above covers the importance of lighting and the effects that water has on light but this still leaves the questions :
How can we create this lighting in the home aquarium?
The best thing, in my opinion, is to ask yourself:
“What animals am I hoping to keep?”
The answer to this question will determine the type of lighting you will require.
The choice of lighting for use in the aquarium depends upon various factors: