Is Blue Light Good For Aquarium Plants? (& How To Use It)

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As an experienced fish owner, I am very familiar with blue light and its role in aquariums. However, until recently I thought of it mainly in the context of fish.

But obviously, there are other creatures in the average fish tank, including live plants. This immediately raises a question: can I use the blue lights with my plants as well?

Since I wasn’t sure how aquatic plants would react to exposure to this color, I started investigating. And after a ton of research, I’m ready to share what I’ve learned.

Is Blue Light Good For Aquarium Plants?

Yes, blue light is good for aquarium plants as it can regulate plant growth, stimulate photosynthesis, and make vegetation denser and bushier. Blue light can also reach the roots of aquatic plants and make fish less aggressive towards plants.

Unlike grow lights, which produce pinkish-whitish light that mimics natural daylight (4,700k – 6,700k), aquarium lights have a multitude of colors, including white, blue, red, and green.

In other words, blue is not a new color to the plants in your tank. If you’re tempted to expose the aquarium to LEDs that only generate blue light, your plants won’t reject the color.

Blue light is good for aquarium vegetation. This is what you should know:

1. Sun Plants vs. Shade Plants

You can’t kill plants by exposing them to excessively bright lights. The plants will only take what they need. But this doesn’t make bright lights harmless.

Intense and prolonged light will boost algae growth, and algae infestations can kill the foliage in your aquarium.

But on its own, intense light cannot harm plants. That being said, you must learn to differentiate between sun and shade plants. 

Sun plants require intense light to thrive. Shade plants are the opposite. While increasing the light intensity won’t harm them, they can easily thrive in low-light conditions.

  • Low-light plants include Anubias Barteri, Rotala Indica, Aldrovanda vesiculosa, Cryptocoryne balansae, Marimo Moss Balls, Brazilian Pennywort, etc.
  • High-light plants include java moss, water wisteria, Heteranthera zosterifolia, Ludwigia inclinata, and anacharis, to mention but a few.

Some people classify blue as a low-light color because it appears dim (especially at shorter wavelengths).

This compels some newcomers to avoid blue light where aquariums with high-light plants are concerned.

However, blue is a high-energy color capable of driving photosynthesis as efficiently as any other color you can imagine.[1] This is true for both high and low-light plants.

2. What Happens To Plants When You Use Blue Light

Blue light is appealing because of the physical characteristics you notice once you introduce the color to a tank, including:

  • The plants are shorter.

Usually, the foliage tries to grow extensions that maximize its ability to collect sunlight.

But even when it appears dim, blue light is still an intense energy source for the plants receiving it.

In other words, the plants in question don’t have to extend themselves during the development stage because they have all the light they need for photosynthesis.

  • The leaves are smaller and thicker.
  • Green leaves are darker. Blue light stimulates anthocyanin production. Anthocyanins produce a red-blue pigment in plants.[2]
  • The stems are strong.
  • The blue light will boost flowering in long-day plants. Expect the opposite in short-day plants.

But why would aquarists care about a color that produces short plants with small leaves?

Well, blue lighting essentially regulates plant growth. Plants can become a menace if you permit them to grow out of control.

Choosing LEDs over regular bulbs will prevent your aquarium from overheating.

3. Blue Light vs. Red Light

Aquarists compare blue and red lights all the time, and for a good reason. First of all, Erik Runkle from Michigan State University has found that red LEDs elongate plants.[3]

They become tall with thin leaves, which some people find appealing. Secondly, red is as effective at promoting photosynthesis as the other colors.

Two factors give blue light the edge:

  • Vegetation becomes denser and bushier in the presence of blue light. 

The color consists of shorter waves that deliver enormous amounts of energy that drive photosynthesis.

  • Blue light is more penetrative. 

It can reach 300 feet in ocean water.[4] You can trust it to reach the roots of your aquatic plants, stimulating growth and allowing the foliage to thrive.

According to Louisiana Wildlife and Fisheries, red and orange are the first colors the water will absorb.[5]

4. Fish Are Less Likely To Ruin Your Plants

You can tell that blue light is suitable for tanks because it essentially mimics moonlight

If blue light were dangerous, fish in the wild would have manifested the consequences at night whenever the moon emerged. 

In an aquarium, blue bulbs will calm restless and stressed fish, which is appealing because calm and stress-free fish are less likely to attack and destroy the foliage.

Nocturnal fish that only emerge at night will appreciate the blue light as they venture out to feed and hunt. 

How Does Blue Light Affect Plants At Night?

Most people use blue light at night. They use it to create a seamless transition between day and night.

The color will promote photosynthesis, allowing the foliage to absorb CO2 and produce oxygen.

How Do I Properly Use Blue Light In My Planted Tank?

  • Identify a duration that benefits the tank’s inhabitants. 

Some people keep the blue lights on for a few hours after sunset. They switch the lights off before going to sleep because they want to give the fish 8 to 12 hours of darkness.

Others keep the blue lights on all night because the color allows nocturnal creatures to hunt without disturbing the sleep of their diurnal (active during the day and asleep at night) counterparts.

Naturally, this approach is not recommended with normal fish, as keeping the blue lights on all night will disturb their sleep.

As I previously discussed, my personal recommendation is to turn the blue light on at 6 pm and off at 11 pm.

Nevertheless, the specific pattern you select will depend on the response you see in your fish.

The standard distance between plants and their lights is 30cm.[6] This provides adequate light intensity.

Don’t forget that bringing the lights closer to the water surface elevates the impact of the heat the lights generate. 

  • Use LEDs. They are energy-efficient. Additionally, they are less likely to raise the water’s temperature. 

Daylight has a color temperature of 6500K. This gives you an idea of the range you should aim for while selecting your aquarium lighting’s color temperature. 

It is worth noting that you normally get a bluish tint from color temperatures as high as 8000 kelvin.[7]

What Color Light Do Aquarium Plants Need?

ColorDo Plants Need It?
Excellent YouTube video explaining how to properly use lighting in planted tanks.
  • Yellow, orange, and violet will make the aquarium more attractive. You can trust them to improve the appearance of your fish and plants. But they don’t matter where plant growth is concerned.
  • Green is equally useless because the plants will reflect it.
  • White can benefit plant life if you use a lot of it because it has some red and blue. Bulbs that replicate daylight are the best option because you get the entire spectrum.
  • Blue is vital to plant growth. The best tone is actinic blue which is barely visible to human eyes.
  • Red promotes photosynthesis in plants. It encourages the production of flowers.

A study from Oles Honchar Dnipro National University, Ukraine, examined the impact of monochromatic light of different wavelengths on aquarium plants.[8]

The plants (Echinodorus quadricostatus, Ceratophyllum demersum) recorded maximum growth when exposed to blue waves.

Red waves produced smaller growth. Does this make blue the best color light? Not necessarily.

The response will depend on the plant. Where possible, get a light that combines red and blue.

What Are The Best Blue LEDs For Aquarium Plants?

The honest answer is that there is no perfect set of LED lights. It mainly depends on what functions you are looking for and what your budget is.

In my tank, I personally use the Hygger Full Spectrum Aquarium Light (Amazon link). I love this product for two reasons.

First, it has a combination of both blue and red lights, which I have found to be the healthiest for aquarium plants.

Second, it comes with a timer, which functions pretty decently. I don’t have to remember to turn off the lights, the device does it for me.

But honestly, almost any set of LED lights will do the trick. There is nothing special about this or the others. Just choose the one that suits you best.

Don’t forget to turn off the blue lights or algae will start running amok.

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If you use blue lights for your aquarium fish, you can rest assured that this type of light is also beneficial for your aquatic plants.

This is because plants are perfectly capable of performing photosynthesis under blue light, which penetrates water quite effectively.

Just remember to turn off the lights before bed. Exposing your tank to blue lights all night will prevent your fish from sleeping and promote algae growth.