Aquarium LED Lighting Terms: Part 3

Posted By: Matt Allen

LED lighting for aquariums

You read about Lumen and Lux in Part 1. Then you learned about PAR, PPFD and PUR in Part 2. The final group of terms we would like to discuss in part 3 of our series about common aquarium lighting focuses on the energy consumed by the light fixture, and how efficiently the fixture uses energy to generate light for our aquariums.

Watt – The watt is the SI unit for power defined as joules per second and is used to describe an energy transfer or conversion.  For a light fixture, the amount of power that is consumed during operation (being converted into both light and heat) is measured as watts and represents energy consumed per unit time.  For most household electrical devices, the wattage (power) rating of the product is in watt hours.  For example, an incandescent light bulb rated as 100W consumes 100 watts of power for each hour it is in operation.

Efficacy – In general, efficacy is the amount of power required to produce a desired effect.  When we discuss efficacy of different aquarium lighting, we are specifically looking at the power consumed by the fixture in watts per unit of light output.  The unit of light output we are interested in depends on our application and may be lumens if we are concerned with visual brightness, or PPF (photosynthetic photon flux) if we are concerned with photosynthesis.  Lumens per watt (lm/w) is a common measure of efficacy for general lighting applications.

Wattage is often used as a metric to compare the performance of different aquarium light fixtures, but as the definition above describes, it only tells part of the story.  As a consumer it is important to understand that the amount of light output generated per watt of power consumed will vary dramatically between lighting technologies.  Just because a product has a higher wattage rating (uses more power) doesn’t necessarily mean it produces more light.  In terms of efficiency and saving on your electric bill, the fixture that produces the most light for the least amount of power consumed would be the winner.

When shopping for an LED aquarium light fixture it is best to work backwards, starting with your specific application to find the right fixture for you, and all the terms we have discussed in these last few lighting posts will help!  If you are primarily interested in visual brightness and color enhancing of the fish and décor you will want to look closely at a fixture’s lumen and lux claims.  If you are interested in growing (or plan to in the future) freshwater plants or corals you will want to consider a fixture’s spectrum for photosynthesis (PUR) and PPFD (sometimes called PAR) claims.  If your aquarium is taller you will want to look at these light intensity claims at different distances from the fixture so you can be sure the illumination will be adequate deeper in the aquarium.  Lastly, consider the efficacy of the light fixture, especially when comparing different lighting technologies (for example LED v. HOT5), to ensure you are getting the best product performance and saving on your electric bill at the same time.

For any technical questions or to discuss the best Elive LED aquarium lighting for you home aquarium please contact us at or 1-855-354-8318.