Blue Light Quantity

[Asa Herring]

I am wondering if there is much knowledge build up about the quantity of blue light in a display tank. With the proliferation of large arrays of LED’s, many people are playing with light balances that are non-traditional.

 

While some people like 14K metal halides or lower and others like 20K’s. More people can now settle on things like PAR levels, after K rate corrections, growth vs bleaching etc. Now that white LED’s are getting more popular, similar discussions are finding some consensus around PAR and other factors. When we move over to blue lighting I haven’t found as much information about blue light.

 

I posted some time back and got more feedback about brands, countries of origin, construction,

efficiencies, heat and other factors. Of course I asked the question in a way that required responses along those lines and they were appropriate for where I was at the time. I was cautioned away from having 50 watt 455nm lamps on a 24 inch deep tank along with MH’s but this is getting to specifics. Right now I am starting from scratch so I want to start in general terms before I turn to the specifics. While I still need schooling in that area, I want to get to just the amounts of blue light and perhaps a little about spectrum.

 

Although I have been reefing for 24 years it’s hard to describe what I am looking for because I am so new to this part of aesthetics. Many people like myself like the look of lots of blue LED’s. In the presents of good metal arch white or LED white light, it can be hard to get a blue overtone in addition to or over the top of the white. For that reason I think, more is better but that might me a bad idea.

 

Of course, there is the pop that ultra-violate light can provide to the fluorescing corals but many people also like a balance that is dominated by the deep blue look of Royal Blue.

 

In addition to something like 420, some of us try to build just the right combination of 450, 455 and 460nm light arrays. To us, they just look brighter, bluer. A large part of this is, in some cases, purely for cosmetic reasons and not for coral growth.

 

In our old tanks, we didn’t add too much white light or we might burn our corals. After allotting space for the white light, we didn’t fill every remaining available square inch of space over the tank with actinics. I didn’t see much difference between a little and a whole lot but not many people told me not to overdo it with VHO or T5 actinic light. Is some cases we were told not to even include actinic light in our total wattage calculations for optimal, safe growth. Now we can burn corals with 420nm LED’s.

 

Now days you can get LED arrays that have 1, 3, 10, 50 watts per lamp and so on. Additionally, you can put hundreds of LED’s in a given fixture. Then there are controllers that change the intensity during the day. Total lighting during the day might be fine while the peaks could be too much.

 

So …. Aside from what kind of blue LED, HOW MUCH BLUE LIGHT IS TOO MUCH.

 

Of course tank depth is a factor and what kind of coral is important but I hope that I can get some feedback on this side of lighting.

 

For reference: I happen to be starting a new 180 gallon tall tank from scratch (72’’Length x 31’’Tall x 18’’Deep). I plan on having a mixed reef. I plan on getting an “appropriate amount of white light be it MH’s or LED’s or both. I am now starting to design my DIY lighting and a little help would be appreciated.

 

I think you in advance.

[Nano sapiens]

Well, you could start here (the bottom graph will give you a quick idea of how much 'violet' to 'blue'):

 

http://www.advancedaquarist.com/2012/10/aafeature

 

...then here to see an actual array built to the specifications

 

http://advancedaquarist.com/2014/4/lighting

 

There's a lot of really good info in these articles.

[farkwar]

I dont think white light is gaining on blue.

 

First gen LEDs were 50:50 white to blue. Now its 33:66 white to blue.

 

The quality of accepted white has changed to eshew cool white LEDs mostly because they are hard to build with high CRI. Warmer whites like neutral whites and even warm whites have made big inroads onto heatsinks.

 

Now ambers and limes are the next "whites " growing in popularity.

 

One day in the future some manufacturer is going to make the equivalent to the Iwasaki 6500K MH bulb with a CRI of 97. And things will be right in the world after that.

[Asa Herring]

Thank you for the articles. I read them both and they were very interesting. It has helped me to fill in other areas of my knowledge about the larger subject. is obvious that I have lots to learn.

 

Unfortunately, I didn’t see much about potentially burning corals with excessive blue light. I saw this in the first article near the end.

 

 

We believe that the most reasonable maximum radiation power should be about 45W/m² for the 400-440nm range and about 40W/m² for the 440-480nm range. Note: Here and above we mention optical radiation power rather than the electrical power consumed by the LEDs. To determine the number of LEDs required in a fixture and their rated current these figures must be converted into electrical power, which depends on the efficiency of the LEDs actually used. These calculations, selection of particular LEDs and other matters concerning the actual construction of a LED fixture will be considered in our next article.

 

It looked like only this paragraph talked about the maximum blue light and violate light, separately. These maximums would be difficult to calculate for me. Even if that was done, I don’t know if they were necessarily talking about a max that burns coral. Perhaps they were. They added in several factors.

 

I don’t know if anyone has actually gone down this road before and have any practical experience with high levels of blue only light that is add to an existing system.

[Horerczy]

You can burn coral with any light color....

[Nano sapiens]

I remember the days of normal output fluorescent tubes (and lots of them!) when things were a whole lot simpler with basically 50/50 actinics and whites. There's a whole lot more choice these days and a lot more knowledge regading a coral's lighting needs.

 

Focusing on the lower part of the visible spectrum, too much light down in the violet and blue ranges has the potential to 'bleach' corals. These wavelenghts promote photosynthesis (good thing), but too much can cause a condition where the coral ejects some, or all, of it's zooxanthellae ('algae') due to too many harmful waste products (think hydrogen peroxide). These wavelengths have high PUR (photosynthetically useable radiation), but our hobby grade PAR (photosynthetically active radiation) meters have difficulty reading at this, and the other end, of the visible light spectrum so it's easy to be fooled by a low PAR reading with actinics. Basically, PUR can be quite high, but PAR can register relatively low in blue light situations and the corals *can* bleach.

 

How much 'blue' is too much? That maximium level can depend on a number of factors such as the coral species involved, how quickly a coral is acclimated, the nutrient content and flow of the tank, etc. That's why most LED arrays have a dimmer function so that an increase of light intensity can be applied slowly (~5%/wk) while PAR is monitored. Blue to white is typically in the ratio of 3:1, or for the really blue look popular these days, 4:1 and both blue and white are usually on separate channels to allow adjustability.

 

Not sure if that answers your questions, but once PUR vs PAR is fully understood (and how and when to use a correction factor when using a PAR meter) it'll all make sense.

[Asa Herring]

Yes that does make sense. Thank you. There are so many factors to consiter!

 

I call a one of the manufacturer and ask basically the same question and he said that normally, you can't put too much blue light into the tank because it is so weak.

 

Let me ask what you think off the top of your head.

 

For my 31 inch deep tanks, do you think that a 50W chip set is to much if slowly turned up to 100%?

I have a 180 gallon tank (72" by 31" by 18") with a 50w chipset on either side.

[Nano sapiens]

31" deep...that's one deep tank! My LED experience is with much shallower tanks, so I'll let someone with this type of experience chime in.

[BradVincent]

My tank is 29" deep and I haven't burned anything. From 2nd hand experience, you burn corals by either:

1) switching from low light to high light too quickly

2) using too long a photoperiod

 

IMO unless you are going well above natural sunlight PAR levels, you won't burn corals from intensity if you acclimate them slowly.

 

Beyond a certain point, more light gives diminishing returns of growth, and eventually slows it down. So the limit to how much is more based on cost/benefit.