How to Measure the Light in an Aquarium

The amount of light needed in an aquarium is dependent on the size of the aquarium and the environment that you are trying to recreate. Lighting requirements will be different for fish-only aquariums, planted freshwater aquariums and reef tanks. It is important to determine the number of watts and spectrum that will work best for your specific tank.

Things You'll Need

  • Paper
  • Pencil
  • Calculator
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Instructions

    • 1
      Flourescent tube light works well for fish-only aquariums.

      Determine the amount of watts per gallon. To measure the total number of watts per gallon, a simplistic equation is used:

      Total watts of lighting/ Gallons of Water = Number of Watts per gallon

      Fluorescent tube light emits a lower output of lumen/watts than compared to a metal halide that emits an extremely high intensity of light radiation. For instance, four to six 40 watt fluorescent tube lights are needed for a 50-gallon aquarium compared to only one 175 watt metal halide fixture.

    • 2
      Lights vary in spectrum. Some contain, blue, red, yellow and green.

      Determine the spectrum required for your aquarium. Lighting spectrum is also important when determining the amount of light needed for an aquarium. Choosing wide spectrum bulbs which emit both red and blue light in the visible spectrum will result in a more realistic and favorable environment for any aquarium.

    • 3
      It is a good idea to keep track of the date the light was purchased. You can also write the date that you replaced the bulb on the light in magic marker as a reminder

      Determine the age of the light bulb. The amount of light in an aquarium is also dependent on the age of the aquarium bulb and where the light is placed. As fluorescent bulbs age they undergo a change that can be harmful to the aquarium. According to Wrobel in "The Living Reef Aquarium Manual," after about a year of operation a bulb will lose up to 30 percent of its intensity and the spectrum will take an undesirable shift. It is therefore important to take the age of the aquarium bulb into consideration.