Photosynthetically Usable Radiation - Sunlight, Metal Halide, LEDs

[Dana Riddle]

This has been an on again/off again project. I used a Seneye 'Reef' device to measure CCT (in Kelvin) and Photosynthetically Usable Radiation for these light sources:
Sunlight - slightly overcast February day at noon, Atlanta, Georgia. CCT = ~6,200K.
Iwasaki 400-watt 'daylight' metal halide lamp. Often proposed to the 'best' lighting source for coral growth by some of the old-timers. CCT =6130K. Lamp burned in 100 hours and warmed up for 20 minutes.
Blue LED (452nm) Orphek Blue Sky fixture. CCT exceeds limit of device.
Aqua LED (496nm) Orphek Blue Sky fixture. CCT = ~13,000K. This light is absorbed by the accessory photopigment peridinin.
Results suggest the blue LED is about 22% more efficient than the metal halide lamp, lending some evidence that LEDs are more powerful photosynthetically.

 

[shred5]

Wow ..

I would never have guessed that it beat the sun..

 

[dantimdad]

Thanks Dana. I think we saw that coming...

 

[dantimdad]

I will say that when @Manose and I were doing testing with the seneye, I noticed that with all channels maxed the bluer lights were in the higher 70s range lending more proof to this.

But, as always, the look the reefer is after is important too. All blue would be just a bit much if you ask me.

 

[shred5]

I will say that when @Manose and I were doing testing with the seneye, I noticed that with all channels maxed the bluer lights were in the higher 70s range lending more proof to this.

But, as always, the look the reefer is after is important too. All blue would be just a bit much if you ask me.

Yea Photosynthesis is only one factor and most lighting has met that for the corals needs. The look of the light and the coloration of the corals are important.
I honestly think we worry way to much about par or pur and spectrum is becoming more important. Unless you have a really deep tank most good fixtures with either t-5, halides or leds are sufficient.

 

[dantimdad]

Yea Photosynthesis is only one factor and most lighting has met that for the corals needs. The look of the light and the coloration of the corals are important.
I honestly think we worry way to much about par or pur and spectrum is becoming more important. Unless you have a really deep tank most good fixtures with either t-5, halides or leds are sufficient.

Agreed.

That's why it bothers me when people down other people for not spending a fortune on lighting. There simply isn't really a need for expensive stuff 90% of the time.

If you like it fine, but don't tell people it has to be that way.

 

[Skep18]

Good stuff.

For us less informed or educated reefers, can you explain what this might indicate as far as the use of LEDs in the hobby @Dana Riddle ?

 

[Dana Riddle]

I will say that when @Manose and I were doing testing with the seneye, I noticed that with all channels maxed the bluer lights were in the higher 70s range lending more proof to this.

But, as always, the look the reefer is after is important too. All blue would be just a bit much if you ask me.

I've got more data to post. The violet LEDs were in the high 80s. Later though. Valentine's Day and too much internet is a bad combination.

 

[Dana Riddle]

Yea Photosynthesis is only one factor and most lighting has met that for the corals needs. The look of the light and the coloration of the corals are important.
I honestly think we worry way to much about par or pur and spectrum is becoming more important. Unless you have a really deep tank most good fixtures with either t-5, halides or leds are sufficient.

This isn't meant to be a thread about 'best' light, but only the ground work for further experiments. The PAM fluorometer will tell the tale.

 

[dantimdad]

What I would like to do is test the Cree CW and 470nm blue on their own to see their efficiency. I'm betting they are both at or below the MH in efficiency. Lending more evidence that these are way over used in commercially available light fixtures.

 

[Dana Riddle]

Good stuff.

For us less informed or educated reefers, can you explain what this might indicate as far as the use of LEDs in the hobby @Dana Riddle ?

It suggests that a PAR value of, say, 200 will not be the same photosynthetically under distinctly different light sources. Research I did in Hawaii found the maximum amount of light required by most corals is about 400 PAR (PPFD, if you will) so the max required under a blue/green combo would be less than that of a warmer light source (such as a daylight metal halide lamp.)

 

[blasterman]

Correct. I have a spectrometer and tired of making this point. Thanks Dana. Corals want lots of blue light coupled with some green light for regulation, and it's too easy with modern LED fixtures to exceed this with optics. If you've been scuba or deep water snorkeling there is almost no yellow or red light to speak deeper than close to the surface.

For the sake of argument I could take a single Cree XPG3, and if I measured it 4" away from the PAR/PUR meter with a 60 degree optic it would brighter than everything else. What's more important is the measurement on a tank over the mean distance of coral depth in the tank.

As for 470nm, if you check readily available spectral charts of artificial light sources halides aren't strong here, and there's no evidence 470nm means more to coral than 450nm. As for the science, I have money on a 465-470 LED producing more energy per watt at that wavelength than halide. Low pressure sodium is really the only wavelength metal halide still competes commercially with, and those aren't much use for growing coral.

 

[blasterman]

Good stuff.

For us less informed or educated reefers, can you explain what this might indicate as far as the use of LEDs in the hobby @Dana Riddle ?

It means that T5 and Halide fans will still claim some psuedo science that LEDs can't grow corals

 

[shred5]

It means that T5 and Halide fans will still claim some psuedo science that LEDs can't grow corals

I do not know anyone who claims they can not grow coral..
Corals are not plants they are animals and photosynthesis is only part of the equation. They are more like farmers. Even light is only part of the equation..

 

[Streetcred]

I do not know anyone who claims they can not grow coral..
Corals are not plants they are animals and photosynthesis is only part of the equation. They are more like farmers. Even light is only part of the equation..

Same here, and I've been around reefing since we used candles to grow sps. Kids these days wouldn't believe it ! ;-)

 

[Dana Riddle]

Correct. I have a spectrometer and tired of making this point. Thanks Dana. Corals want lots of blue light coupled with some green light for regulation, and it's too easy with modern LED fixtures to exceed this with optics. If you've been scuba or deep water snorkeling there is almost no yellow or red light to speak deeper than close to the surface.

For the sake of argument I could take a single Cree XPG3, and if I measured it 4" away from the PAR/PUR meter with a 60 degree optic it would brighter than everything else. What's more important is the measurement on a tank over the mean distance of coral depth in the tank.

As for 470nm, if you check readily available spectral charts of artificial light sources halides aren't strong here, and there's no evidence 470nm means more to coral than 450nm. As for the science, I have money on a 465-470 LED producing more energy per watt at that wavelength than halide. Low pressure sodium is really the only wavelength metal halide still competes commercially with, and those aren't much use for growing coral.

We should compare notes!

 

[Flippers4pups]

Excellent work Dana! Can wait to see the rest of the study. At this point with my experience with use of LED'S, confirms my growth results. So far exceeds my previous experience with other light sources.

This is purely anecdotal on my part, but I'm truly sold on LED's capability to grow healthy coral. As stated, there are many other factors in successfully growing healthy coral that must be met and maintained for long term success.

 

[dantimdad]

OK @Dana Riddle Valentine's day is over. More numbers!

 

[Ron Reefman]

I will say that when @Manose and I were doing testing with the seneye, I noticed that with all channels maxed the bluer lights were in the higher 70s range lending more proof to this.

But, as always, the look the reefer is after is important too. All blue would be just a bit much if you ask me.

And just because the blue spectrum from leds looks good, it does NOT mean you can't run enough white leds to make the tank (corals) look very natural. IMHO it doesn't even take that much white led to make a tank look natural. And that white doesn't mean the blue has gone away or somehow disappears. It's still there for the coral's zooxanthellae to use.

 

[DSC reef]

It means that T5 and Halide fans will still claim some psuedo science that LEDs can't grow corals

I'm a halide and T5 user and don't claim that. Maybe don't put everyone in a box that uses a particular light? I love led, halide and T5.