Will Algae Grow Under Moonlight Bulb? {Will It Stop Algae From Spreading?}

Are you using moonlight bulbs for your aquarium? Are you concerned that you can still get algae blooms under these low levels of light? In this article, we’ll find out if algae grows under moonlights bulb lighting.

Will Algae Grow Under Moonlight Bulb? Algae growth will be limited under Moonlight bulb, but may not stop growing if there are nutrients in the water readily available. Plants will outwork algae for these nutrients while algae eaters will chomp away at what is left over and weakened under the low level light of Moonlight bulb.

Why Is A Moonlight Bulb?

A moonlight bulb is a great addition to enclosures or aquariums. They provide low levels of lights and some heat without disturbing the diurnal cycles of your aquatic life. Moonlight bulbs are used for reptiles, amphibians, invertebrates and fish.

Shy or timid aquatic life that prefer to hide during the day may become more visible and open to venturing out under these calming lights.

Why Use A Moonlight Bulb?

Up to 90% of the light energy from a moonlight bulb contributes to warming infrared rays. The heat provides thermoregulation in enclosures. The benefit and appeal in aquariums are as follows:

  • peaceful and calming
  • encourages shy or timid aquatic life to swim in the open
  • doesn’t affect diurnal cycles
  • emits beneficial warmth 
  • aids in healthy metabolism 
  • limits algae growth

While a moonlight bulb cannot claim to completely inhibit the growth of all types of algae, it helps to reduce the spread and overgrowth of algae blooms.

Should I Use A Moonlight Bulb For My Tank?

Would you like to view your aquatic life at night without disturbing their rest? Nocturnal viewing is made possible with a moonlight bulb.

Your aquatic animals’ day and night cycles will continue as normal. If you would like the lighting to look more blue and appealing, you can use blue tinted glass for your tank as well.

The moonlight bulb is low wattage and doesn’t interfere with your plants and corals as well. You can still use regular tank lights during the day if you wish.

Does Algae Grow Under Moonlight Bulbs?

Certain types of algae such as Red Turf Algae or Black Beard Algae can still grow under a moonlight bulb. These types of algae grow near the bottom of aquariums and lower depths in the wild.

Blue light or moonlight penetrates through the water. A low setting and wattage is necessary to limit the growth of algae.

If you wish to prevent the growth of algae you will need to provide more than a moonlight bulb. Look to add more plants to outcompete algae for available nutrients.

Many kinds of algae of algae will experience a slower growth under these low lights. The important thing to consider is where else your algae is finding nutrients such as phosphates. A lack of CO2 or not enough planted areas contributes more towards algae growth.

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Does Algae Need Light To Grow?

Yes. Any low light including moonlight bulbs could be utilized by algae to remain alive, but low lighting will slow it down. You will need to act further by limiting the oxygen it receives when there are no plants competing for what is available.

Plants will outwork the algae and absorb more of the available nutrients through the gases in your tank that are present from water circulation and detritus.

Limit feedings to your aquatic life and remove leftovers. Perform frequent water changes up to 50% per week even if you are using a moonlight bulb.

Will Algae Grow Under LED Lights?

LED lights limit algae growth and affect the growth of nuisance algae compared to regular aquarium light. Moonlight bulbs are similar as they are low level light emitters.

Lighting that is high in yellows and greens can increase algae growth more. Use blue lights or moonlight bulbs that are purple or black in color for limiting algae growth.

Can Algae Grow Under Artificial Light?

Algae can continue to grow under artificial light as long as there are nutrients available in the tank.

LED lights can continue to allow enough lighting for algae growth under predominantly reds, yellows and greens more than blues.

Moonlight bulbs produce good results, but cannot claim to stop algae growth.

Do Bright Aquarium Lights Cause Algae?

Bright lights alone cannot create algae blooms. If there are plants, high CO2 levels, low phosphates and algae eaters in the tank, they will help negate the effect of bright lights.

Nevertheless, do not light the tank for more than 12 hours a day. Moonlight bulb lighting can remain on at night as the low level wattage doesn’t disturb the diurnal cycle of aquatic life.

Algae growth will be stunted, slowed or stopped altogether when it’s starved of nutrients.

Does Blue Light Feed Algae?

Blue light alone does not feed algae without nutrients in the tank from gases, phosphates and ammonia.

Clean tank water that is changed weekly can deplete nutrients for algae growth. When blue lights degrade and their Kelvin rating is lowered, it may lead to more algae growth.

Does Blue Light Stop Algae Growth?

The photosynthesis that algae needs to grow and thrive is reduced with blue light. Red-yellow spectrum of light drives algae growth far more.

Corals enjoy blue lights as it emits to deep water much easier. UV light, moonlight and blue LED light are helpful in limiting algae growth.


A Moonlight bulb can hinder or prevent the spread of algae compared to regular lights. They are not the perfect tool to stop algae growth. You need to starve algae of tis available nutrients in the tank first and foremost.

Secondly, you can employ algae eater to help reduce algae in the tank. Moonlight bulb lighting is appealing to keep on at night and it penetrates deep into the tank where some forms of red or black beard algae can still benefit from it.


Thank you for stopping by at HelpUsFish.com. We have plenty of articles on a wide variety of aquatic life that may also pique your interest. See you again soon!

Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.

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