Do LED Lights Cause Algae Growth?

In Aquarium Lightingby PaulK

There is a lot of speculation that the blue light or moonlight setting in LED lights will cause algae to expand in your fish tank. This is due to blue light being the spectrum of light (380-500nm) that algae use to grow. The truth is that there are a lot of factors that can contribute to algae growing out of control. As far as lighting is concerned, all lighting spectrums could contribute to algae growth, not just the blue moonlight setting. If the conditions are right for algae to grow, then you will see algae in your tank. Leaving the LED lights on too long would most likely be the culprit.

If you leave your aquarium lights on for too long of a period of time, that will promote algae growth. This includes the moonlight setting, so the aquarium lights need to be fully off at night. Between fluorescent and LED lights, LED lights cause less algae growth.

Use a timer to prevent that from happening.

Just because you have a bunch of different color options on LED lights, doesn’t mean you have to use them. Quite frankly, they’re sort of gimmicky. Just full-on and full off white light is sufficient. No more than 8 hours on at a time.

Things that contribute to algae growth in your aquarium:

  • Lights left on for too long. Set your timer for 6-8 hours per day.
  • Direct sunlight. Keep your fish tank out of direct sunlight
  • Dirty aquarium. Algae feed off of the food and other organic waste. Clean your aquarium often with frequent water changes and substrate vacuuming. Don’t overfeed your fish.
  • Too much phosphate. Increasingly, cities are infusing phosphate in tap water to prevent lead and other chemicals. Use a phosphate filter in a reactor or your aquarium filter.
  • Unhealthy live plants. Use strong lighting and nutrient-based substrate so the live plants will outcompete the algae for nutrients.
  • Too many nutrients.
  • Lack of water circulation in the fish tank. Get a wavemaker in conjunction with a good filter.

Bright LED lights can actually be beneficial in that they will help promote healthy live plant growth. If the LED is too bright however, that can cause some algae growth. When you have healthy live plants, they tend to hog all of the nutrients that algae need to grow keeping the algae growth to a minimum.

You want to be in the 6500K range for good plant growth and no CO2 injection.

So if you’re going the low budget route here and you have a planted freshwater tank with no CO2 injection the Finnex Stingray 2 is a great option.

The Nicrew Classic is also a good low budget option.

If you have a higher budget, this Fluval Plant Spectrum is a beautiful light. is a participant in the Amazon Affiliate Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to

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