What's with blue light?

[Valentini89]

I use LEDs and use an even 50/50 blue/white mix, and turn the lights off around 10pm but I plan on running all blues at night on my new tank. What I don't understand is why ppl run all blue lights during the day. You can't see your tank inhabitants as well as if it were a blue/white mix. Someone enlighten me.

[fishkeeprian]

I use LEDs and use an even 50/50 blue/white mix, and turn the lights off around 10pm but I plan on running all blues at night on my new tank. What I don't understand is why ppl run all blue lights during the day. You can't see your tank inhabitants as well as if it were a blue/white mix. Someone enlighten me.


I believe corals absorb more of the blue spectrum during photosynthesis. They have evolved to do this due to the sun penetration through the water. This is why most reef tanks you see will have more of a blue look to them.

[ReefkeeperZ]

420-460 nm wavelength is a photosynthetic range of the light spectrum, and blue light travels through water farther than any other color (that's why water with a white sand bottom looks blue it's the color that can make it to the bottom and be reflected back up for our eyes to see)

I would not recommend running blues all night. 24 hours of photosynthesis wont do your corals any favors (and algae can use it to photosynthesize)

the more blue your light mix the deeper water you are imitating, the whiter red green yellow the shallower

[Ron Reefman]

Just because your eyes can't see the blue light when the white lights are on, doesn't mean it isn't there. And that is the main color spectrum that the coral's zooxanthellae use to do photosynthesis which in turn feeds the coral.

If you are going to run blue light all not (probably not a good idea) have them turned down as low as you can get them. It's probably a good idea to have the tank full dark for at least 6 hours over night.

[Nick30G]

Here's another weird thing I have found with blues in my New tank... when I am running blues only (whites completely off) my clownfish pair goes nuts and the female starts chasing and attacking the male. When I turn the whites back on, they are both completely fine. From a few Google searches, it seems that the female cannot identify the males color band around his head because it looks different under blues. Therefore I have to run whites and blues at the same time lol.

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[oldhead]

One thing I have found since switching to leds is my torch is much more colorful. Funny thing is I have a frag off of the main colony that I put higher in the tank and that has less color.

[Timfish]

What is often overlooked is too much blue light is detrimental. It is used for photosynthesis but the bright fluorescing colors corals make is often an attempt to get rid of too much blue light. Like Reefman said make sure your corals have a period of total darkness and keep the moonlights very low.

[sde1500]

Definitely don't run them all night. You should allow your corals plenty of time in total darkness. They don't get light 24/7 in nature, so don't give it to them in your tank. As for why more or all blues during the day? Have you seen a tank full of brightly colored corals in only blue light? They pop like crazy. That is why. I don't do blue only, but there are 2 hours on each side of sun rise and sun set that is blue only and I love it, the colors are ridiculous.

[Valentini89]

Thanks for all of your input!

[Psychomantix]

My tank only has blue lights, I see my reef inhabitants just fine.

[Uncle99]

There needs to be a consistent photoperiod for the corals, blue for photosynthesis, white to see stuff, and so fish can see stuff....your burn out any corals with 24 blue...

[jacksonpt]

Interesting read... thanks for posting the question, and thanks to everyone for responding.

My LFS, who I generally trust, told me the last time I replaced my T5 bulbs that color/temp was more important to corals than was PAR numbers. It was the first I'd ever heard that, and this thread seem to support it, at least as far as the importance of the blue spectrum.

[Tripod1404]

This is the absorption spectrum of chlorophyll. You can see it has two main absorption peaks; one around blue/violet and one around red. Red light does not penetrate too deep, so for most corals the major light source is blue/violet.

https://www.giss.nasa.gov/research/features/201311_kiang/fig3_324.jpg

[ktownhero]

I used to wonder the same thing, but now I really can't stand my tank to be lit visibly "white". Leaning toward a bluer visual spectrum just adds a crispness to the tank that you don't get otherwise, and helps some of the colors of all creatures in the tank really pop. I'm not talking about running like an actinic-looking tank all day, but I really like about a 14k spectrum as my peak with 20k as my ramp up/down goals and my sunrise/sunset to be actinic.

[organism]

I don't think OP is referring to running blue lights all night, only at night.

What is often overlooked is too much blue light is detrimental.

I ran only blue lights 12 hours a day for 2 years as an experiment and had incredible colors and good growth. It is not detrimental. These days I have 20% whites on for 4 hours a day and the other 8 hours are blue.

My tank only has blue lights, I see my reef inhabitants just fine.

This guy gets it :)

What it comes down to is some people prefer a windex tank for better coral colors and some don't. To each their own. Personally I'm not a fan of the super washed out look of tanks running 50/50 spectrum, I figure you paid for coral colors and paid for lights why not set your lights so you can maximize colors.

[Tripod1404]

Interesting read... thanks for posting the question, and thanks to everyone for responding.

My LFS, who I generally trust, told me the last time I replaced my T5 bulbs that color/temp was more important to corals than was PAR numbers. It was the first I'd ever heard that, and this thread seem to support it, at least as far as the importance of the blue spectrum.

PAR is photosynthetically active radiation. It is a lot more important to than the color of the light. Color just shows the wavelengths produced by that bulb and how it would look to our eyes.

A daylight MH lamp will look white/yellow but it might still have more or equal blue wv light in it compared to a cool light T5. It just gets washed out because our eyes are more sensitive to yellow than blue. But that blue is still in there, just not visible to us. Chlorophyll will still absorb that wavelength.

So a daylight MH has higher PAR than say an equivalent cool light T5 because it produces are broader spectrum. Even if they had equivalent PAR just at blue wavelengths, daylight would also have PAR from red and others.

This is why warm lights are good for growth and cool lights are good for aesthetics.

[Valentini89]

OP here, soaking in all this knowledge....