To what extent do white LED's contribute to PAR?

tnc112105 · May 10, 2020

Thinking of upping the blues on my older generation ReefBreeders Photon 48 V1 to add a little more "pop".

Changes of course will be done very slow and in a controlled manner to not cause shock to the corals.

Most of what I have seen and/or read has indicated that when tuning your lights, you should tune your whites to look pleasing to the eye. Will a 10% increase in blues and 10% decrease in whites result in the same PAR? To what extent do white LED's contribute to overall PAR?

Thanks in advance.

Ron Reefman · May 11, 2020

I ran EverGrow led fixtures for years(EverGrow makes Reef Breeders Photons and they were virtually the same). Now I've been running Photon v2 and v2+ fixtures. But I worked for another led company that also had their fixtures made by EverGrow, and I'm quite familiar with the fixture and the light they produce.

All visible light will add to PAR. But PAR isn't the only thing to consider when it comes to your light. PUR (Photosynthetic Usable Radiation) is what's important, but you can't really measure PUR as every coral and plant has a different combination of light spectrum that make up that individual species PUR. What we can say is that most zooxanthellae in our corals use way more blue spectrum in their PUR than any other spectrum (most terrestrial plants and even other algaes use more red spectrum). So running more blue than green, yellow, orange or red is good for the photosynthesis your corals need. And remember that white light is a mix of at least red, green and blue.

So depending on the mix of spectrum you are currently running, adding more blue is probably a good thing. Reducing the white by the same amount isn't a bad idea, but unless you are going such a high PAR that you are close to bleaching some corals, the reduction of white may not be necessary. And corals do need other spectrum besides blue to produce other other chemistries like amino acids and pigments.

So you have the older Photon V1 fixture. Just to be clear, that's the one with only 2 channels of control, right? So what levels are you currently running at peak midday?

My suggestion would be to run roughly twice as much blue as you run white (with the red and green). Personally, I like the color pop I get from corals that fluoresce. I pick corals based on that criteria more than anything else. Therefore I like the fact that they show better under blue spectrum. So I run my Photon V2+ at almost 3 times more blue than white (90% on 2 blue channels and 35% white and only 5% on red and green). But that's just for 6 hours of midday lighting (which is intense enough to produce photosynthesis). I also do a much more blue 4 hour sunrise and a 5 hour sunset. The corals pop much more, but the PAR is lower due to less power and there is little if any photosynthesis going on.

tnc112105 · May 11, 2020

Wow, thank you SO much for your thorough and informative reply! Yes, this is the V1 ReefBreeders with only 2 controllable channels. Midday I'm running about 35 blues, 25 whites. I know it sounds super low, but way back when when I had the light over a 55g, this was more than enough to get good growth, and there were warnings abound about "frying" corals under ReefBreeders because they were so powerful. However, for the past few years over my Reefer 450, the growth and color has left something to be desired. I contacted ReefBreeders last night and they also said that the light may not be putting out the same intensity it was 5-6 years ago, which is another reason I'm looking to ramp things up.

Ron Reefman · May 11, 2020

You are welcome.

I'm going to guess at 35% blue and 25% white your best PAR under the light at 10" deep is about 150. That's more like what you want at the sand out near the glass. I run 2 Photon V2+ fixtures over my 36x30x20 tank (I need 2 to cover 30" front to back). I run 90% blue and 35% white and at 10" deep I get a PAR of 300+.

Here is an idea for you to try. I call it 'The Canary in the Coalmine'.
Get a small frag of an inexpensive plating coral like a red cap monti. Mount it however you want to so it's at the highest, brightest spot in your tank. Now start turning your lights up by 5 percentage points on one or both channels every week for 6 to 8 weeks. OR, until the monti frag bleaches... I'm betting it won't. And if it does, dial back the power by 5% on both channels and you be good. IMHO, with your fixture you could easily acclimate your corals over 2 months to run at 80% blue and 40% white... probably more, but lets be conservative.

Just remember, TAKE YOUR TIME!

tnc112105 · Jun 2, 2020

So I got a little bit of a late start on making light adjustments due to corals showing signs of stress. I was not able to pin down the cause, but it seemed to resolve over about a week after running some carbon.

I also rented a PAR meter from BRS. I have the meter until Thursday. You were right @Ron Reefman. There were some hotspots, which I attributed to the light being too close to the waterline (6"), but the PAR overwhelmingly did not break 170 at most of the locations that I measured.

The corners and sides of the tanks were also brutally low (9-20 PAR). To be fair, it is a 4ft light on a 5ft tank, so I decided to raise the light up another 4" to get a little better spread and use the PAR meter to find a setting that generated slightly higher PAR readings than what the corals were getting previously to start acclimating them to a higher light. A few examples:

I went from 40B/32W @ 6" to 60B/40W @ 10" above water line

Vivids Acro: 150 PAR @ 40B/32W to 168 PAR @ 60B/40W

Grafted Monti Cap: 125 PAR @ 40B/32W to 150 PAR @ 60B/40W

Raja Rampage Chalice: 115 PAR @ 40B/32W to 120 PAR @ 60B/40W

Bubblegum Digitata: 180 PAR @ 40B/32W to 180 PAR @ 60B/40W

I don't think I'm moving too fast, but some of the corals look terrible. The Bubblegum digi hasn't put out polyps in 3 days, and yet the PAR for this coral hasn't changed. One Acro frag even RTN'd. And yet others are completely unfazed. I knew it likely wouldn't be a seamless transition, and I expected a little discontent while they were acclimating, but I am concerned. The light settings were changed 72 hours ago (Saturday morning). Stay the course? Or move the distressed corals to a lower light?