Led Lighting

[Crazy fishes]

I am very much interested in finding out about LED lighting and was wondering if anyone knew much about them. I have recently been shown a website theLEDguru.com and was looking through the product list. A number of questions came to mind:

1) How do LED compare with metal halide units (with regards PAR)?

2) Is it an option to use them solely for a reef tank setup?

3) How well do they penetrate the water? How far do they produce 'useful' PAR? 2 feet or just the top few inches?

4) Is the lighting schedule of the same duration?

I am sure more will emerge over time but that is enough for now....

Regards

 

[nanocubeking]

I dont know much about LED's but I do know that they will penatrate extremely deep. I dont think Its just traditional led's though. The only led lightiing system I know of is Solaris. It is a bada$$ system but crazy expensive system too.
http/www.solarisled.com/

 

[raptorrex]

given the motivation you can make a very good LED system for much less than the Solaris unit, even add a control unit. and still have enough left for a good second hand car. have a look at the specialist electronics forums, the tend to be full of good ideas. if you show a bit of knowledge, they give lots of help too.

 

[SkiFletch]

LEDs can certainly be used to light a reef aquarium. Their benefits are obvious; low electric consumption, low temperature, and the obvious longterm $$ savings that comes with. The drawbacks are high initial setup costs, and very specialiazed wavelengths which must be chosen carefully.

As nanocubeking mentioned, there is currently only one commercially available lighting unit for marine tanks. The solaris system uses very high-output LEDs. Each LED lamp in the Solaris system is a 4watt LED. They claim to (and subjectively seem to) replicate the amount of PAR you get from a 400watt metal halide with half the energy use. And with 50,000 hours of life in the lamps, bulb changes are a thing of the past with LEDs. Their penetration is very good and their "cone" of light more resembles that you'd get from a 6xT5HO setup. By that I mean they put out even amounts of light whereas halides have more of a high-power in the center under the lamp, diminishing as you go out.

Those LEDs from theLEDguru.com are 1/4 watt LEDs probably. They are smaller both physically and electrically. Thus, you'd need more of them to achieve the same amount of light from something like the Solaris system. Then however you run into the spectrum problem. Those LEDguru lights output light in the 465nm range. Zooxanthellae tend to prefer 455nm light. 465 will "work" but not very well, you really need to find 455nm LEDs. Then, you can feel free to do as boboboy says and DIY your own fixture.

 

[Colin_T]

What is PAR?

 

[andywg]

Photosynthetically Active Radiation.

From looking at RC, it would appear that the LEDs are very good, but that a decent 250W MH will give better growth at the moment.

Some very good results are being recorded with Luxeon LEDs plus HO T5 tubes. You do need to put heat sinks and the like on the luxeons to make sure they work perfectly. Actually replicating the Solaris from DIY is no easy task at all.

The issue with the smaller LEDs is being able to get enough of them close enough together. If you dom't mind burning them more often you can overdrive them a little.

I also seem to recall that overdriving T5 gives some interesting amounts of light too.

 

[Crazy fishes]

Colin, PAR is an acronym for Photosynthetically Active Radiation and it represents the 'visible light' area of the electromagnetic spectrum; 400-700nm wavelength. This is the area which the photopigments in the zooxanthellae can absorb from. In actual fact, each of the numerous pigments they use ,chlorophyll a, chlorophyll c2 etc have peak absoptions and this is represented by the term Photosynthetically Usable Radiation (PUR) which is a fraction of PAR. The fact is when looking for a light unit we all look at the power of the bulb/lamp and temperature; these are functions of a decent light system but not the whole story apparently. The crucial thing to have is an appropriate amount of PAR at the various different depths in the tank so that the zooxanthellae are happy.

Hope this helps

Regards

 

[Colin_T]

thanks andy and crazyfishes, interesting reading.

So do fluorescent and metal halide have the appropriate PAR for aquarium plants and corals?

It's only a matter of time before more companies start to research and make LED light units. When that happens the price should start to drop and the quality improve rapidly. After all, LED units have only been around for a couple of years. Fluoros and halides have been around for many more.

 

[SkiFletch]

Yes, they most certainly do output enough PAR to grow corals. Obviously different flouros and different halides will output different PAR.

 

[Colin_T]

Does it say what the PAR is on the light globe box/ packaging?

 

[andywg]

It's very rare that a full PAR breakdown is given. I am fairly sure that RC has done a comparison or few on different bulbs.

 

[steelhealr]

Any one have time to comment for the audience on 'lumens'? SH

 

[andywg]

Lumens? Well let's start with Wiki:

The lumen (symbol: lm) is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.

NHow, the important part there is regarding it being adjusted for human eye sensitivity. The human eye sees very well in the yellow to green areas of the spectrum (shown quite well in this article). Now plants tend to want more in the blue and red parts of the spectrum, so while you could have a very high output of lumens on the light, it could all be in completely the wrong parts of the spectrum to aid coral growth.

An interesting look at power vs lumens vs PAR is in the link below:

light comparisons

Edit

On the subject of LED vs MH, an interesting page is this one. Every time I see things like this I think that LED is the way forwards, but I do recall seeing some comparisons on RC where a decent 250W bulb was better than the MH, and T5s did extremely well too. Obviously, now I want it, I can't find the thread...

Also, an interesting look at how different lights give off their light, and a mini glossary are here.

 

[will8]

i have just got a tropical marine centre LED light. the TMCaqualight 500 added to my 4 T8. only been in to hobby 6 months so i dont know how they are. will they be ok for polp corals.

 

[Musho3210]

If you want to see what the best bulb for your fixture (MH) is on terms of PAR output and/or spectrum and/or electricity used, then sanjay has some good calculators and information .

Ballast does matter, you can get a Chinese made piece of 80% lead junk for very cheap, or you can go with a high quality, big PAR output light ballast and get the most out of your light as well as have lasting technology (cough cough PFO).

I'll use my light as an example:

250 watt EVC ballast
12K Reeflux bulb single ended
I'm also running a REALLY good expensive reflector which also matters a lot, but sanjays calculators dont add in reflector.

anyway with that, i get on average 54 par per foot diameter and my fixture runs at 269 watts making my fixture 0.2022 efficient (i believe fluorescents run at about .18 efficiency?)

Lets change it a bit, lets say i use a PFO HQI ballast, id be getting 74 par per foot diameter but i would be overdriving my bulbs at 335 watts on a 250 watt fixture, which means less of a bulb life.

Anyway, feel free to mess around on his calculators [URL="http/www.reeflightinginfo.arvixe.com/index.htm"]http/www.reeflightinginfo.arvixe.com/index.htm[/URL]


The bulb matters a whole lot too. Lets say i have the EVC ballast, if i ran a EVC 250W 10000K DE 1 bulb, id be getting 119 par per foot diameter at 272 watts and .4404 efficiency, less of an overdrive, better par. The PFO with the same bulb can get 179 par per foot diameter though, again, at overdriving.