How High Should I Hang / Mount My Aquarium Light?

One of the most frequent questions we get is “How high should I hang my light over my aquarium?”. And it’s an important question to answer.

Mounting a light at the proper height can make a big impact on your coral. Mounting an aquarium light too low creates shadows and less light gets to the edges. It also creates a hot spot directly under the light. On the flip side, mounting an aquarium light too high leaks light all over your floor – wasting energy and depriving your corals of the PAR they crave.

There is no simple answer for this question. Since aquarium sizes can vary dramatically and there are so many different types and sizes of lights, there’s no surefire answer. However, we have a procedure that can help.

Our favorite way to determine the ideal height is a step-by-step process that you can use for all types of lighting, including T5s, LEDs, LED-T5 hybrids and many others. Follow the simple steps below to find the right height for your unique setup.

  1. Do your best to completely darken the room where the aquarium is located, except for the aquarium lighting.
  2. Raise the light well above the aquarium, perhaps as much as 24 inches.
  3. Pay attention to the “edge” of the light on the floor. It should be fairly obvious with most lights, due to reflector or optic performance.
  4. Slowly lower the light until the edge of the light is captured within your aquarium (rather than on the floor). Make sure the edge of the light output is completely captured within the aquarium

This height will fill the aquarium with the most light, reflecting off the glass to reach under overhangs and outcroppings, especially when the glass is clean.

Higher PAR can be achieved by lowering the light a bit further, however doing this will also reduce the amount of light reflecting off the wall of the aquarium, thereby reducing the amount of light under overhangs and outcroppings.

This procedure works great for all ATI fixtures, including the SunPower, Dimmable SunPower, and LED Powermodule, as well as other popular brands, such as AquaIllumination, Ecotech Marine Radion, Kessil, and many more.

So, no matter what your brand, type or model of light fixture, we hope this helps you find the ideal height for your aquarium light fixture.