Why Blue So Low?

[MuddyWaters]

Why does seemingly everyone keep the blue spectrum low on lights? Is it aesthetics or some other reason?

 

[Essjay]

It encourages algae growth. In planted tanks, plants need both red and blue light, preferably with some green as well, to flourish. If there's too much blue and not enough red, aquarium plants don't grow well. But algae can use just blue light so in the absence, or reduced amount, of red light algae will flourish at the expense of the plants.
In a non-planted tank it will still encourage algae, as will every part of the spectrum.

 

[MaloK]

It depends on the setup and plants used.

If you have a shallow aquarium with low light requirement plants, without floating ones... You will tend to lower blue and red light... to give an effect of cover...

If you have a tall aquarium with floating plants... They will regulate the lightning for the lower less needy ones and at some point you might be forced to raise the levels to maintain sufficient penetration.

In my Cases Too much red promotes red algae on rocks at the bottom and too much blue promotes Hair / Green algae. on the plants mid level..

I'm still playing with the light. But I'm pretty sure It can emulate any condition I want.

At the moment I'm running a 12watt LED at 30%w, 15%r, 30%g, 15%b. on a 8.5 inch tall tank.

And it still seems a little too strong.

 

[Uberhoust]

Plants need many frequencies of light to grow to their full potential. Focusing on Blue and Red does target the main chlorophylls found but there are many other pigments plants use that absorb different frequencies that play a smaller but still significant role, example Carotene which helps the chlorophyll function correctly. The main color not used extensively is green, which is why it is reflected by the plant's leaves (it's not absorbed and as such cannot provide energy for any process).

That said, I normally try to get a more balanced light because aesthetically full spectrum light is the most pleasing to see the fish and plants by. You might target different light regimes if all you were doing was growing plant biomass.

 

[MuddyWaters]

Thanks all. I do have blue lower than the others. I raised red as high as the white and warm, but might lower it some. The lights I have come with an out-of-the-box setting for planted tank. I may go back to emulating that more for color distribution since I have no clue LOL.