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14.4.1. Light Spectrums

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Author : David Bogert

Published :

Time To Read :
4 minutes

Before reading this post it is best to go to this link and read the over-all article on aquarium lighting:

14.4. Aquarium Lighting

Aquarium lights are used to illuminate the aquarium fish. What few recognize is that the intensity of a fish’s color is determined to a strong degree by the lights over the aquarium. To illustrate this, it is necessary to put up the spectrum of most lights and their effect on aquarium fish colors.

spectral distribution of sunlight
spectral distribution of sunlight

This is the spectrum of sunlight. The effect on colors is:

ItemEffect on color seen or photographed
  
Electric blue fryerigood
Green Plantsbright
Yellow Labidochromisbright
Orange Goldfishbright
Dragon Blood Peacockbright

This is what our eyes are accustomed to and where photography is the easiest. It is unfortunately difficult to create in the aquarium.

Spectral distribution of fluorescent tube
Spectral distribution of fluorescent tube

This is the spectrum of a typical fluorescent tube. The effect on colors is:

ItemEffect on color seen or photographed
  
Electric blue fryerigood
Green Plantsdecent
Yellow Labidochromisdull
Orange Goldfishgood
Dragon Blood Peacockgood

This was what we used to use for aquariums.

Cheap Shop Light Spectra

Spectral distribution of LED Shop light
Spectral distribution of LED Shop light

This is the spectrum of an LED bulb typically used in a house or shop. The effect on colors is:

ItemEffect on color seen or photographed
  
Electric blue fryeridull
Green Plantsbright
Yellow Labidochromisbright
Orange Goldfishgood
Dragon Blood Peacockdull

This is decidedly not the best lamp to use for plants (plants require blue and red-light spectra). This is also the spectral curve of the inexpensive aquarium LED fixtures with only white light elements. An interesting combo is to combine a cheap in-home LED bulb rack as 70% to 80% of the light with a small grow light LED as 20% to 30% of the light. This should give very close to a sunlight spectrum and bright on all the items.

One Popular Aquarium LED Light Spectra

Spectral distribution of LED Aquarium light
Spectral distribution of LED Aquarium light

This is the spectrum of one popular LED set up for aquariums. The effect on colors is:

ItemEffect on color seen or photographed
  
Electric blue fryeribright
Green Plantsgood
Yellow Labidochromisgood
Orange Goldfishdull
Dragon Blood Peacockdull

This is not a good spectra for much of anything. It will give a blue tint to everything and it won’t grow plants very well. But it illustrates the pitfalls inherent in buying aquarium lights.

Spectra of Another Aquarium LED Light

Spectral distribution of LED Aquarium light
Spectral distribution of LED Aquarium light

This is the spectrum of a 60% white, 20% blue and 20% red LED used in an aquarium. The effect on colors is:

ItemEffect on color seen or photographed
  
Electric blue fryeribrilliant
Green Plantsdull
Yellow Labidochromisgood
Orange Goldfishbright
Dragon Blood Peacockbright

This is the best light for a typical aquarium (including mixed plant and fish aquariums) and can be achieved with most moderately priced aquarium LEDS.

Spectra of a Reef Aquarium LED Light

Spectral distribution of LED Reef Aquarium light
Spectral distribution of LED Reef Aquarium light

This is the spectrum of reef aquarium LED light. The effect on colors is:

ItemEffect on color seen or photographed
Electric blue fryeribrilliant
Green Plantsdull
Yellow Labidochromisdull
Orange Goldfishdull
Dragon Blood Peacockdull

Many freshwater hobbyists get these by mistake. You can tell when they put their photos up on social media. They all have a distinct blue tinge.

LED Aquarium Grow Light Spectra

Spectral distribution of Aquarium grow light
Spectral distribution of Aquarium grow light

This is the spectrum of a LED grow light for a planted aquarium. The effect on colors is:

ItemEffect on color seen or photographed
Electric blue fryeribrilliant
Green Plantsdull
Yellow Labidochromisdull
Orange Goldfishdull
Dragon Blood Peacockbrilliant

Now this is the strongly violet tinged light seen in advertisements for grow lights. These are the best lights for growing plants. This can be seen by looking at the absorption spectra for a green plant:

Absorption Spectrum of Plants
Absorption Spectrum of Plants

Plants absorb light only in the blue and the crimson red area of the spectrum if the light is low to moderate. Some plants can absorb energy in the orange, green and scarlet portions of the spectrum if the light is VERY strong. Blue light combines with crimson light to give violet light. Therefore grow lights are violet tinged.