Lighting PAR

[Eric Alvarado]

This has probably been asked a thousand times, but has anyone seen a comparision of lights?

i.e. PAR values of T5s, vs. LED vs. Metal Halide vs. VHO? etc.

[Timfish]

Eric, part of the problem with finding comparisons is the variation there is between different manufacturers and and sometimes the same manufacturer. Dana Riddle has some good articles on AdvancedAquarist.com and Drs Feldman and Joshi have some excellent research as well. My own experience using a lux meter (lots cheaper and still good for comparing two different tanks to match lighting levels for a coral or for monitoring drop in light output as a bulb ages) shows more than 30% variation between two different MH bulb manufacturers with the same color temp bulb, reflector and ballast. One of the articles by Dr. Sanjey Joshi monitored coral growth for 14 months and showed different corals grew better under different lights ie what one coral liked another didn't. If I remember correctly someone recently posted in one of the forums they had a PAR meter they were willing to loan out.

[Eric Alvarado]

No, I am aware of that. But each technology has a range of values - even if it varies. Obviously there is a lot more such as color spectrum for photripic response, photosynthetic response, and chloryphil response. However, some people rely on "watts per gallon" or "PAR value" or PUR Value, etc. I have seen nothing that even tries to compare them, so choosing lighting is at best a guessing game. Do you go with MH, LED, PC, VHO, etc. How can anyone choose anything without knowing or having some basic method to compare the technologies.

What I want to know is as follows:

What is the average PAR for T5

What is the average PAR for MH

What is the average PAR for PC

What is the average PAR for VHO

Additionally, I know that the length of the bulb seems to play into how deep it can penatrate water, but would 2 24" bulbs give the same light a 1 48" bulb?

I know LED differs radically, but given whatever numbers on above, you could potentially take reading and compare. But to compare, you need at LEAST a basic understanding of how much light each technology generates.

[+mcallahan]

Timfish really nailed that there are so many variations, to name averages really tells you nothing.

For example, with MH bulbs, putting them under a single reflector (one long piece of metal) drastically reduces their PAR. Put them under a parabolic reflector, and your PAR numbers will be much higher.

Choosing lighting is so much dependent on your budget, heat issues, needs of the tank, etc that I feel choosing a lighting setup is really custom for each tank.

[Eric Alvarado]

By that reasoning, I should go with 1 12" PC light over my 125G because it is too complicated to bother discussing. It's not really that complicated. X PAR should be required per whatever creature, and say, a 250 MH light gives out 300-500 PAR 12" below the water on average. Each technology does put out a certain amount of light, that clearly can vary given reflectors, temperature, etc.

If I knew coral X like "X PAR" and "Light technology X" gives out X to Y PAR. People always are trying to be EXACT, but clearly you don't need to do that. You need rough estimates and then go with the technology that best meets your need (tank size, arrangement, hood-nohood-etc). But in order to do that, you need basic numbers even if it as simple as 3-5x- Watts per gallon for SPS.

i.e. I've been looking at LED strips. But in order to know how many I might need, I clearly need to understand how much PAR each strips gives out. Additionally, it would be useful to see how much PAR is being generated MH lighting, or T5HO, or PC lighting that is successfully growing the same things I want to grow. It's NOT too complicated to figure out, it is a base gathering of information that is spread out all over the place but not located in a single location.

I was simply asking if anyone knew of a resource that had any information like this that would give someone an idea of what tech to use for what. It is really not that complicated. I know I've seen PAR ratings for all kinds of technologies, but I have never seen them side by side, and never with regards to what corals need what level. (i.e. Most LPS need 75PAR+, keep below 300 or bleaching). I know these statements are broad, but they provided needed starting points.

[+mcallahan]

well I can tell you haven measured the PAR in my tank, I've decided any guideline numbers are useless. I've got 2 RBTA living happily under 25 PAR. I've got SPS coral growth very quickly under 80 PAR.

I've never seen a guideline of numbers for each type of lighting and if it did exist, I'd hope whoever measured it all was charging for the information as it would take a lot of time.

[Eric Alvarado]

hmm.. doing a bad job explaining, because I don't think it is all that complicated

All the critters already have "low, medium, high" notes about their needs. It's listed on every website. That said, what PAR rating would be considered "low, medium, or high." Or is PAR not the thing to review? I'm being very general, not overly specific about the exact needs of every creature.

I'll see if I can gather information on PAR values for the different technologies. Would love to see your PAR meter run against some VHOs and T5HOs and see what it reads.

[+etannert]

I smell a future episode of Mr. Saltwater Tank TV...

[Timfish]

Eric, here's a place to start, it's an article by Sanjey Joshi comparing select LED, MH and T5 fixtures.

http://www.advancedaquarist.com/2010/2/aafeature2

Additionally I would suggest looking at research by Dana Riddle and Sanjey Joshi. They both have published a great deal on Advanced Aquarist. Between the two of them there's something like 40 - 50 articles in current and past issues and some of them include reviews of LEDs and I know Dr. Joshi did one other comparing several LED fixtures side by side with a MH. There are certainly other articles by other researchers and you should find more on other websites like Reef Central and Wet Web Media. Callahan is right guidelines are totally useless. Some corals are adaptable to a wide range of lighting conditions and some are not. I have Frogspawn in less than 1000 lux (est. 50 PAR) and in 20,000 lux (est. 400 PAR). Porites porites in the wild is found from the surface to 160 ft while it's close sibling Porites branerri is only found from 15 - 30 ft. You ask some very good questions about coral growth and bleaching but what makes it very difficult to answer is we don't have any way to easily measure both the intensity and spectrum of the light field (fluorescing proteins are sensitive to just one wavelength so even a slight variation in spectral output between bulbs with the same PAR may alter the color of a particular coral). It is also difficult to determine the saturation point of the zooxanthellea a coral is using, any light above this point is wasted. There are also different species of zooxanthellea and two specimans of the same species of coral may utilize different species of zooxanthellea and may react very differently to changes in light and again this is something difficult to determine. Your questions really highlight the importance of researching your corals to help insure they will do well in a tank and the importance of a club like this where you can connect with people who are already keeping corals under similar conditions.

[Eric Alvarado]

Thanks Tim and Mark.

I still think 99% of the lighting descisions are made with some basic assumptions Metal Halide light work for SPS is an assumption. PC lighting is best for softies and LPS, etc. What I want to know, is how many T5 or which LEDs or how does VHO stack up against MH. Can these technologies, and in what volume, do they compete with MH lighting? Do the low end LEDs stack up against VHO or T5 or MH?

I read the article link, good reading. Little hard to dig through all those articles, and I get distracted in every edition. Appreciate the pointer. Would have replied earlier, but work has been hectic, and I've been pretty out of pocket.

Thank you

Eric

[Timfish]

Eric, Here's some readings of light levels in one of my tanks. I think it presents a good example of why it's so hard to give "guidelines" to lighting in aquariums but hopefully it may give you a better idea of how much lighting you may want to achieve the "look" you want for your tank. The lighting is a 12000K 250W HQI MH bulb in the center with 14,000K 250W HQI bulbs on the sides. Bulbs are in Lumenmax Elite fixtures with Lumatek electronic ballasts. The tank was initially set up with 400W mogul base MH with a generic reflector but testing on another tank showed the Lumenmax Elite 250W HQI fixture put out more light (10 - 20% to the corals) so the fixtures were replaced. You can see in the picture the green slimmer has pretty much the same colors under a wide range of light intensity, from about 180 to 650 PAR (8,000 to 30,000 lux).

Unfortunately the actual colors do not show well in this picture but there are two colonies of the same A. millipora coral (the one on left is a frag of the one in center) with very different coloration. The one in the center is directly under the 12,000K bulb and is yellow and pinkish-orange with just a little bit of green and is getting about 450 PAR (20,000 lux). The 2nd on the left hand side is at the same depth but is partially shaded by a cross support of the tank and is getting about 250 PAR (12,000 lux) from a 14,000K Bulb and is almost completely green.

[Eric Alvarado]

Thanks for that Tim, gives me some basic numbers to think about. Will post the PAR readings we took on the new Vertex lighting after I get my T5s ballas warrantee repaired.