How To Determine What Aquarium Lighting You Need

When the decision has been made that keeping a marine aquarium is for you the next decisions are what animals you want to keep and what equipment you will need to use.

One of these decisions is what type of lighting you should use above your aquarium.

It is my opinion that realistically there are two options available to guide you towards your decision:

  1. Choose lighting which is appropriate for the animals which you hope to keep
  2. Choose animals which are suitable for the lighting you have made the decision to purchase

Some people think that this is a strange way to decide however to me it makes perfect sense (but then in my head various things make perfect sense!)

Basically you can go out and purchase some lighting which is relevant to your budget and then design the remainder of your aquarium and livestock purchases around this lighting or you can design your aquarium system including the lighting around the livestock you want to keep.

For example if you have purchased a second hand aquarium system and this aquarium comes with T5/T8 fluorescent lighting and is 18 inches deep from top to bottom then realistically you are looking at either a fish only aquarium or a reef tank with soft corals and perhaps some long polyp stony (LPS) corals.

Another example following this trend would be purchasing a complete aquarium kit from your local fish shop where the lighting is included. In this example metal halide lighting is provided and the aquarium is 24 inches deep from top to bottom. In this example you could again keep a fish only aquarium or a reef tank with either soft corals, long polyp stony (LPS) corals, short polyp stony (SPS) corals or a mixture.

In the second example above if the decision was made to keep a fish only aquarium then the lighting will be overkill as a fish only aquarium does not need intense lighting for the welfare of the aquarium inhabitants. On the same scale if SPS corals were decided upon then other items will also be required to ensure that the aquarium is suitable. Strong water circulation springs to mind.

If lighting is being chosen based upon the aquarium inhabitants which in my opinion is a better way then the following can be used as a guideline:

  • Fish Only – T8 Fluorescent Lighting
  • Soft Corals – T5/Power Compact Lighting
  • Hard Corals – Metal Halide/ LED Lighting

The above is definitely not set in stone as there are other variables which need to be taken into consideration the most important of which is the depth of the aquarium from top to bottom however this is normally only the case when corals are being kept.

If a fish only aquarium is your aquarium of choice then effectively all you need to do is provide lighting so that the fish can see and a dusk/dawn cycle can be created. This allows for the fish to be confident in its home as well as allowing you to see it.

When corals are being kept they require, dependent upon the species of coral strong lighting. Coral use the lighting as an energy source which allows the coral to thrive and grow as long as its other requirements are met for example calcium and water movement to name just a couple.

If you have an aquarium which is 30 inches deep then you will require stronger lighting than if you had an aquarium which is 18 inches deep.

The reason for this is the actual power of the lighting. Lighting power is measured in wattage – the higher the wattage the stronger the lighting will be.

If you had an aquarium which was 18 inches deep then quite probably a 150 watt metal halide would suffice to provide adequate lighting for hard corals to be maintained.

On the other hand if you had an aquarium which was 30 inches deep then a 250 watt unit or perhaps even a 400 watt unit would suffice to provide adequate lighting for hard corals to be maintained.

Wattage power in lighting is important as we want to ensure that the light unit has enough power to punch the light right to the bottom of the aquarium without losing colour. The deeper the light has to penetrate into water the quicker the colour from the spectrum is lost.

It is feasible that hard corals could be maintained in an aquarium that was 30 inches deep with a 150 watt metal halide unit however the corals would have to be placed in the top third of the aquarium.

Aquarium lighting is quite a complex subject especially when it comes to discussing the colour spectrum therefore I am not going to go into this in this post. Effectively at this point you want to try and push as much of the light right to the bottom of the aquarium.

One thing you do not want to do is allow light to not go into the aquarium. By this I mean allowing the light to go over the top of the aquarium into the surrounding room or allow it to be ineffective light due to a badly designed reflector.

Reflectors are used to direct as much light as possible from the bulb down into the aquarium. There are some designs which due to their design reflect a lot of the light back into the bulb itself rather than down into the aquarium which therefore means wasted light. A good reflector will reflect light around the bulb and down into the aquarium. The majority of good quality aquarium lighting units nowadays come with good quality reflectors but it is something you should be aware of.