The lighting demands of a Reef Tank are far greater than that of a Fish Only With Live Rock setup. So when choosing a light for your reef tank, consider the following:
- Light Spread. When we speak of light spread, we are speaking of the area which a light covers.
An easy way to demonstrate light spread would be to take a flashlight, turn it on and stand it on end with the light facing down on a table. Now, slowly pick it straight up, moving away from the table. Notice that as you move the flashlight further from the table, the area of the table covered by light increases. The growing and shrinking of the area covered by light on the table based on the distance from the table is the spread.
So when selecting a light, the spread must cover the footprint of the tank. And much in the same way you adjusted the spread of light on the table top by changing the distance of the light from the table, you can adjust the spread of your light by changing the height at which the light hangs over the aquarium. But there is more…
- Light Intensity. It isn’t enough that your light spread covers the entire footprint of your tank. It must do so with the proper light intensity as well.
When speaking of light and it’s intensity in aquariums, people will reference light measurements in “lumen” or “PAR”. What is the difference between PAR and Lumen? Generally, lumen are used to measure the brightness of light as perceived by the human eye.
PAR is the amount of light that is actually available to be used during the photosynthesis process. So when speaking in terms of PAR, we are speaking about the portions of the light spectrum usable by the inhabitants in the tank.
