salty joe
Active member
I have heard that ultraviolet is beneficial for corals, but always anecdotally.
Do you know of any studies or any hard evidence that ultraviolet light actually is beneficial for our tanks?
how efficient are LEDs really?
- Thread starter salty joe
- Start date
I have heard that ultraviolet is beneficial for corals, but always anecdotally.
Do you know of any studies or any hard evidence that ultraviolet light actually is beneficial for our tanks?
mr.wilson
.Registered Member
UV radiation improves colour intensity (through promotion of UV blocking agents) not growth, so my use of the term "beneficial" was self serving for the aquarist who is looking for bright colours. Too much UV can cause dynamic photoinhabition which retards the photosynthetic process thus slowing growth.
Dana Riddle has written some good articles on the subject.
http://www.advancedaquarist.com/2007/2/aafeature/view?searchterm=coral uv
Dana Riddle has written some good articles on the subject.
http://www.advancedaquarist.com/2007/2/aafeature/view?searchterm=coral uv
Sanjay
Premium Member
Just came across this thread. Interesting read.
Wanted to clarify a statement in my article, that really should have been fixed on proof reading.
"From this it should be quite clear that statements directly touting LEDs as being equal to 250W metal halides are correct"
This statement really needs to read as follows:
"From this it should be quite clear that statements directly touting LEDs as being equal to 250W metal halides are correct as far a peak values of PAR are concerned". The later part of the paragraph states that the area coverage should also be taken into account.
Other than coverage, which is a function of better spreading optics, number of LEDs and their spacing, I feel the current generation of LEDs are more than adequate for reefs.
Look for some more test results of other LEDs in the near future.
sanjay.
Wanted to clarify a statement in my article, that really should have been fixed on proof reading.
"From this it should be quite clear that statements directly touting LEDs as being equal to 250W metal halides are correct"
This statement really needs to read as follows:
"From this it should be quite clear that statements directly touting LEDs as being equal to 250W metal halides are correct as far a peak values of PAR are concerned". The later part of the paragraph states that the area coverage should also be taken into account.
Other than coverage, which is a function of better spreading optics, number of LEDs and their spacing, I feel the current generation of LEDs are more than adequate for reefs.
Look for some more test results of other LEDs in the near future.
sanjay.
Mustang Boy
New member
for those that mentioned the lack of UV there are UV LEDs although tey do cost more than the regular blue and white LEDs that most of the DIYers use
also sanjay i think it would be interesting if you tested a DIY array in the same type of experiment as you did before.
also sanjay i think it would be interesting if you tested a DIY array in the same type of experiment as you did before.
Agu
Premium Member
Just to point something out that was mentioned in passing, LED lighting is a semiconductor technology, as such it's really in it's infancy. I suggest you review Moores Law ( which is applicable in this case) to realize how fast this technology is changing and improving. Growing cost effectiveness and a substantially smaller environmental footprint makes LED lighting the lighting of the future.
Comparing current lighting to LED technology is like comparing a horse and buggy to a Model T. Sure there was a lot wrong with a Model T and you had to be brave (and resourceful) to drive one but it was a completely different way to acheive the end result of transporting people/goods. Eventually the horse and buggy went into history along with the buggywhip. ( Had to throw in a bad cliche )
Just like a Model T, in the future if you want to see an incandescent bulb you'll have to find an antiques collector or visit a museum. They'll be right next to the antique fluorescent bulbs :lol:
Comparing current lighting to LED technology is like comparing a horse and buggy to a Model T. Sure there was a lot wrong with a Model T and you had to be brave (and resourceful) to drive one but it was a completely different way to acheive the end result of transporting people/goods. Eventually the horse and buggy went into history along with the buggywhip. ( Had to throw in a bad cliche )
Just like a Model T, in the future if you want to see an incandescent bulb you'll have to find an antiques collector or visit a museum. They'll be right next to the antique fluorescent bulbs :lol:
mr.wilson
.Registered Member
Is LED the horse & Buggy or the Model T
We all agree that there is great potential in LED, but the versatility may not be as limitless as some believe. In my opinion they are aesthetically a great replacement for fluorescent lighting (cool, eerie & clinical looking), but until they look like the sun, or at least MHL, they are a hard sell for me.
solos2
New member
Is LED the horse & Buggy or the Model T
We all agree that there is great potential in LED, but the versatility may not be as limitless as some believe. In my opinion they are aesthetically a great replacement for fluorescent lighting (cool, eerie & clinical looking), but until they look like the sun, or at least MHL, they are a hard sell for me.
Have you seen how bright the 50w LED bulbs are?
Go to youtube and search for "50w LED" and see for yourself.
mr.wilson
.Registered Member
I guess I'm reading your data wrong, as you state with regard to 250 watt MHL...
"Peak values of PAR achieved were 278 micromoles/m2/sec at distance 24" from the center of the lamp, and 190 at 30" from the lamp center.
And with respect to the LED Eco-Lamp KR92, that you have decided to use on your own tank...
"Peak values of PAR achieved were 224 micromoles/m2/sec at distance 24" from the center of the lamp, and 160 at 30" from the lamp center."
I realize that the LED fixture is using only 110 watts, and the MHL is using almost triple the watts at 306, but we are talking about fixture comparisons, spanning a certain area. According to your data, the MHL fixture covers 36" x 30" (1080 sq"), and the Eco-Lamp KR92 covers only 24" x 18" (432 sq") which is almost a third of the area. Am I reading the data right that it takes three LED fixtures to match the coverage of MHL, thus negating the energy savings, and still falling 25% short with PAR values? Further, the LED unit needs to be mounted 30" over the water to reach this coverage, so we are looking at 160 PAR at the surface before anything is lost with diffusion and turbidity in the water. I'm assuming that the MHL fixture coverage was tested at a conventional 6-12" above the water.
The MHL test light was fired with a generic ballast so a premium electronic ballast would offer a 30% energy savings, but to be fair, der_wille_zur_macht has suggested that the Eco-Lamp KR92 is far less efficient than current LED offerings.
Am I missing something?
Someone mentioned that the lack of a significant heat transfer allows you to mount an LED fixture much closer to the surface of the water, but we are limited to 6" or so do to salt creep/spray and even more so by coverage/spotlighting. Unless the LED bulbs are a homogenous colour governed by an RGB controller, I can't see how the reflector design can blend the colours naturally and uniformly.
mr.wilson
.Registered Member
Have you seen how bright the 50w LED bulbs are?
Go to youtube and search for "50w LED" and see for yourself.
I could only find a few on Youtube, mostly for pot plants. The light looked eerie and artificial. Many people like the look of fluorescent lighting, but to me it looks like pharmacy lighting. It's just my personal opinion.
Mustang Boy
New member
the LEDs sanjay tested were commercial fixtures that are using inferior bulbs to what the DIYers are using and the bulbs are much closer together because they are a lower wattage. with the new 3w LEDs like the cree we are able to space them 2in apart and not have spotlighting and actually get some great PAR and MH beating PAR with the use of optics and being able to mount them closer to the surface than you can a mH
JMO, but i think it's a little tough to compare MH to LED, especially in regards to coverage area. For LED's coverage area can vary so much depending on light spacing, lens type, mounting height. Also, because of the cone-like dispersion intensity can vary significantly within the dispersion area (even more significantly depending on lens/optic type). For instance, i have 160ish watt LED mounted at 26" above the sand bed. At that height and at 100% load i measured ~600 PAR on the bottom directly under center, and 285 PAR 8 inches off center at the bottom. But when i take the lens off i have less than 280 directly under center. With that kind of variablity it seems tough to do an apples to apples comparison.
As for the heat part, i think you're correct that in theory you could mount the LED's right on top of the water, because the projection of heat into the tank is not as high as MH, but it would be self defeating in terms of coverage area and the spotlighting effect.
mr.wilson
.Registered Member
Those PAR values are much more encouraging. To be fair, I don't put as much emphasis on a wide spread as most hobbyists do, so a narrow spread isn't a deal breaker. As long as the corals and rock structure is illuminated, casting excess light on glass walls and substrate is counter productive with respect to nuisance algae growth. In my opinion, it's just hype that causes people to hang large reflectors over tanks that are only 24" wide. Sometimes less is more.
I actually pitch the MHL fixture back a few degrees at an angle to cast light toward the back (reef) to minimize shadows and direct light away from the from glass and onto the reef. Fish and corals look better and photosynthesis is aided. I find this to be a better use of the coverage ray so smaller European & Chinese fixtures are as efficient or better than oversized units that would cast light behind the tank (over the top trim).
Now is there a way LED can evolve to look more like natural sunlight? or does one need to install small/supplemental 20-40 watt incandescent lights to get shimmer, shadows and a warmer look? Would these supplemental incandescent lights be drowned out by the LEDs? Is there a mechanical way with a fan blade circling under the LEDs (between the bulb & the water) that would cause a flickering/shimmering effect while cooling the fixture & the tank?
TheFishMan65
New member
As I understand it. LEDs do produce a shimmer. Especially with a lens. The shimmer is caused by a point source of light. The tighter the lens the more it simulates this. There are some videos that show this - don't know where one is off the top of my head.
As for a warmer look. You could use warm whites and have the same color as incandescent. All the DIYers (including me) are trying to get to 14k-20k look, because we understand that wave length is better for the aquarium.
[EDIT]
Use an LED flashlight (probably any flashlight) and you can see shimmer.
[EDIT 2]
Quick search and a found a youtube video
http://www.youtube.com/watch?v=TVUfIatAXoE
They only used one LED, but as I understand it (and hope) it will work with more
As for a warmer look. You could use warm whites and have the same color as incandescent. All the DIYers (including me) are trying to get to 14k-20k look, because we understand that wave length is better for the aquarium.
[EDIT]
Use an LED flashlight (probably any flashlight) and you can see shimmer.
[EDIT 2]
Quick search and a found a youtube video
http://www.youtube.com/watch?v=TVUfIatAXoE
They only used one LED, but as I understand it (and hope) it will work with more
mr.wilson
.Registered Member
Thanks for the video, but I believe that overlapping bulbs cancel out the single point of light effect. A partially shielded T5 bulb would also cast a shimmering effect, but the sun and MHL are unique in having a true single point source. LED as it is today, offers more like what George W1 would call "1000 points of light"
"I will keep America moving forward, always forward -- for a better America, for an endless enduring dream and a thousand points of light. This is my mission. And I will complete it." George H.W. Bush
I've got a couple 24 LED DIY fixtures with 60 degree lenses, and they definitely do produce shimmer, despite the overlapping light cones. Haven't run MH in a long time, but it seems to me the shimmer effect is a little less than I was getting with a single MH bulb, but still VERY obvious.
I don`t understand why no one has set up a proper control tank- a six foot tank with LEDs on one end MH on the other. Same frags on both sides- dark no mans land in the center. People keep trying to act scientific about this subject- without science entering in to the equation.
Because not all of us can afford to set up a secondary 6 foot long tank just to test out some lights. We work with what we have. If you have the means to do so, go for it. If i could afford to setup a 2nd tank adequate for SPS and light testing i would have just bought a commercially available unit.
