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PAR readings from a 2x250W MH setup


mcallahan

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I measured these with an Apogee MQ-200 meter on the "electric" setting. The water pumps were turned off.

The values seem low to me. What is really weird is the higher PAR reading on the corners near the sandbed vs. half way up the tank. The only thing I can think to attribute that too is my arm being in the way of the meter receiving all the light it could.

Lighting: 2x250W 20K Reeflux bulbs driven off Lumatek e-ballast

Reflector: Single reflector. It's an old Coralife MH fixture. There is a single pane of 1/8" glass on the bottom of the fixture.

PAR_90g.jpg

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Its your reflector I bet. People don't realize how important good reflectors are, you can lose 50% of your lighting with a crappy reflector. Most aquarium fixtures do not seem to be designed by a photometrics engineer, they are just a couple of bends on a piece of polished aluminum. When you look at high quality gardening reflectors there are multiple bends in order to completely use the available light....even the best reflectors can only direct about 85% of the light making it usable.

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I think you are right Stephen. Mine is a single reflector.

Not gonna go build a canopy and get some individual reflectors tho. I'll do LEDs instead!

So you have one fixture to fit 2 bulbs? Is the reflective material salt stained or corroded? That also makes a big difference. Does it have glass? Is it permanelty stained too? Clean glass alone decreases lumen output by 10%, just imagine what a dirty glass and tarnished aluminum reflector decrease it.

Why don't you already have LED's? Wouldn't that sell them the best? ;)

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I think you are right Stephen. Mine is a single reflector.

Not gonna go build a canopy and get some individual reflectors tho. I'll do LEDs instead!

So you have one fixture to fit 2 bulbs? Is the reflective material salt stained or corroded? That also makes a big difference. Does it have glass? Is it permanelty stained too? Clean glass alone decreases lumen output by 10%, just imagine what a dirty glass and tarnished aluminum reflector decrease it.

Why don't you already have LED's? Wouldn't that sell them the best? ;)

That's right, 1 single reflector. It isn't salt stained but I do have a a piece of glass between the bulbs and the water. The glass is clean.

One thing is for sure when I switch to LEDs, I going to need to acclimate my corals as the AI SOL unit put out 2000 PAR right below the fixture and 600 right below the water level! (I'm not switching to AI units, I just used it as a frame of reference)

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so am i just chopped liver,POS reflectors=POS results. didnt need a meter for that. i would imagine that my #s would be about the same since i have a homemade POS light set-up, im surprised that anything will grow under my reflectors. I shld have spent $2000-$3000 on a manufacture light that i wouldnt have been happy with. JMobservasion. I enjoy all u bring to the reef club and support you in all your adventures, these are truly astounding findings i would have never thought.

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so am i just chopped liver,POS reflectors=POS results. didnt need a meter for that. i would imagine that my #s would be about the same since i have a homemade POS light set-up, im surprised that anything will grow under my reflectors. I shld have spent $2000-$3000 on a manufacture light that i wouldnt have been happy with. JMobservasion. I enjoy all u bring to the reef club and support you in all your adventures, these are truly astounding findings i would have never thought.

so this quote will probly be taken the wrong way BUT...call me when you get up. I had the making for a LED fixture and got rid of it cause i wasnt sure what i was doing or if they would support my tank. I am wanting to conserve POWER,HEAT, and looking for LONGEVITY. you seem to know about the SOL fixture and thats what i was lookn at but just dont know. would 4 of them be enough?

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so am i just chopped liver,POS reflectors=POS results. didnt need a meter for that. i would imagine that my #s would be about the same since i have a homemade POS light set-up, im surprised that anything will grow under my reflectors. I shld have spent $2000-$3000 on a manufacture light that i wouldnt have been happy with. JMobservasion. I enjoy all u bring to the reef club and support you in all your adventures, these are truly astounding findings i would have never thought.

lol, even with POS refelctors you are getting light in the tank....so things will grow. BTW my fixtures were pretty inexpensive at $95 each, just because they are expensive doesn't mean they are any better. What matters is that they have plenty of room inside the reflector, which most aquarium fixtures don't have, in order to focus the light down. If the light bulb isn't deep in the fixture your light cone gets larger and more light is wasted on the outside of the tank. A perfect example of this is the first set of reflectors I put on my tank. They were about the same price as the refecltors that I have now but were still POS. They let out too much light from the sides of the fixture and didn't direct as much in the tank. My new reflectors with the same bulbs and ballast were much brighter...I even have some before and after pics somewhere.

I had a reflector designed about 2 years ago that I haven't been able to afford to put in production yet. The reflector was designed by a photometrics engineer using $10k software called photopia which was created to design efficient reflectors. I spent thousands of dollars having this done and I even had quotes for as high as $10k for the same project. It took him weeks to get the design exactly right, its not a simple process. Hours of an engineer time and special software is what it takes to truly make a fixture efficient. You and me aren't capable of that without the software. Even just the slightest bend will make a big difference in the way the light bounces off the metal. I'll give you another example of a problem with homade reflectors or ones not designed by engineers. There is an area right above the bulb that if the reflective material is flat...it can damage the bulb. There must be a "V" made in to the reflective material with the point of the "v" above the center of the bulb....running lengthwise with the bulb. What happens is when this area is flat first of all you are losing all of the light that is coming from that area because it simple bounces right back in to the bulb. When this happens the bulb is heated up significantly, the lights UV rays pointed back on itself is not good at all for the bulbs. That causes them to wear out prematurely from overheating. If it were a higher wattage of bulb it would burnout after a few weeks...I've seen it happen plenty of times with gardeing reflectors and 1000 watt bulbs. BTW the best reflectors have rounded sides. The bulbs are round and put out light in a round pattern. Squared reflectors do not fit the shape of our bulbs...hope that makes sense.

Do you really want LED's? Your tank is doing sooooo well, I would hate to see you be a test pilot for heavy sps tanks and LED's. As far as your reflectors go there is no way you are getting all that your bulbs can offer...but if it ain't broke don't fix it, seriously.

I attached a product design video of my reflector so you can check out the shape of it, I think that the link will work. Click on the zip file, then click on the only file inside, click run. Allow to go online to view it. Once its open press the "PLAY" button for the video to start. As you can see the shape of the reflector is different than any aquarium reflector you have seen on the market. The reason why reflectors aren't made this way now is because its cheaper to make them the way they do now. This reflector wasn't designed for aquariums, its made to put a 4' x 4' square pattern on the floor at 36". An aquarium reflector would need to be smaller with a smaller footprint, it would take a whole new design for that.

air-cooled demo video.zip

post-1255-0-12455700-1303061654_thumb.jp

patent drawing.pdf

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Hydro,

Very good technical discussion on lighting reflectors. Consider that lighting is the single most expensive componant of reef keeping, I think it is over hiped. If money is not an issue, light it up. I have been using PAR meters for ten years. Because I have always tried to mix outside lighting with my growout tanks, I have never fused with light spectrum, I like 6500 kevin. Enjoy the LED. I have always liked MH with the glimmer lines associated with single point lighting. Are the glimmer lines evident with led's?

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  • 2 weeks later...

So Mark came out and brought his PAR meter. I use daystar reflectors and had the 14k plusrite bulbs. I was actually getting 3x's as much light at the surface of the water and my readings in the tank were much stronger too. Marks reflector is a name brand reflector and should be comprable to the quality of what I'm running but it its not close. I was actually surprised at the difference, goes to show you what a good reflector will do for you.

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cool, i need to buy me one of those there meters. Now im curious how my reflector is working. What did your #s look like?

I'm curious too. Just under 1000 about 12" below the bulb and 160 at the bottom of the tank, Mark probably remembers better than I do.

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That's about right Stephen. I was impressed at how much PAR you were getting at depth. My PAR fall off is very steep. The bottom on my tank was in the 25-30 range. Funky tho - my RBTA is happy down there.

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My other thought is that LEDs will do fine on my tank. Clearly you can grow SPS coral without a lot of light

Sure there are some high light LEDs out there but from my PAR readings you can see that tons of light isn't the answer.

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You should put the LED over your tank and redo all of the PAR readings with it, then you would know if you were getting more or less with the LED. I know they have pretty high PAR at the waters surface but what about at the bottom of the tank?

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cool, i need to buy me one of those there meters. Now im curious how my reflector is working. What did your #s look like?

I have one on order that I'll make available for loan.

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You should put the LED over your tank and redo all of the PAR readings with it, then you would know if you were getting more or less with the LED. I know they have pretty high PAR at the waters surface but what about at the bottom of the tank?

I'll post up my PAR numbers after my meter gets here. I'm using LEDs.

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