Coral reefer said:
See that's the problem with LEDs, too many blanket statements that really are not true at all. As it stands the BEST LEDs you can buy right now (not the press released products that Cree is testing) are slightly more efficient (lumens per watt) than the most efficient MH lamps. While its true we don't use those color temperature MH bulbs over our tanks (more yellow end of the spectrum), those who use LEDs toss in those blue LEDs as well which are no where close in terms of efficiency as the white ones, so overall the efficiency from that standpoint drops as well. Then there's the fact that most LED setups you can buy just don't use the best that are out there, at best they use "last generation" best, and at worst, they use the 3rd party knock off to reduce costs on the product. I can't argue with manufacture claims that a 48watt unit = the same output as a 250w halide simply because they probably took the best/worst case scenario... and quite honestly probably fudged the results.rygh said:
Heats the room AND tank more though. Yes I'm counting on some of that inefficiency to heat my tank.
sfsuphysics said:See that's the problem with LEDs, too many blanket statements that really are not true at all. As it stands the BEST LEDs you can buy right now (not the press released products that Cree is testing) are slightly more efficient (lumens per watt) than the most efficient MH lamps. While its true we don't use those color temperature MH bulbs over our tanks (more yellow end of the spectrum), those who use LEDs toss in those blue LEDs as well which are no where close in terms of efficiency as the white ones, so overall the efficiency from that standpoint drops as well. Then there's the fact that most LED setups you can buy just don't use the best that are out there, at best they use "last generation" best, and at worst, they use the 3rd party knock off to reduce costs on the product. I can't argue with manufacture claims that a 48watt unit = the same output as a 250w halide simply because they probably took the best/worst case scenario... and quite honestly probably fudged the results.rygh said:
Hmm. I will try to be careful on my wording on this, since I both agree, and disagree.
Comparing top end MH with junk-LED is not really fair, yet it is true.
Like I mentioned above, and you state, what you get off the shelf for LED is rather weak, and some has some
really cheap Chinese crap LEDs in it. If you see "Prolight", run away. Might be Korean. Whatever.
On the other hand, MH has really been refined through the years, and a nice electronic
ballast and US/Euro/Japanese bulb is really state of the art.
If you are saying MH is theoretically as efficient as modern LED, head-on, sorry, go away.
And that specifically means comparing true light energy output versus electricity in.
Even in the not always useful lumens/watt, LEDs are 120-139, where MH are usually 70-85.
Data sheets numbers are pretty easy to measure. Not fudged.
Regarding the color/efficiency argument and blues:
(And in this case - ignoring the junk-leds.)
The problem really is a data sheet issue. LEDs are rated in lumens or sometimes mW.
Rating the blue end in lumens is nearly useless. Since it is a function of the human eye, and we don't see that very well.
Rating in mW is great, but how do you compare it??
So they ARE actually very efficient. Just hard to tell.
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Overall, the LED "can" do a fantastic job. It is great at converting electricity to light at a given tight frequency.
Way way way better than MH.
*IF* you hit that wavelength correct, it is a huge win.
So if coral was a one-wavelength animal, and you hit it, that 48W -> 250W is probably an understatement.
But clearly coral is not.
SO : It comes down to color!!!!
If you get the right mix of blues, with a bit of red and other spectrums, you win. If not, you lose.
But if that was not bad enough : The human eye color responsiveness is not even remotely the same as coral photosynthetic needs.
Hence the endless problem of mixing and matching of whites/blues/reds/cyan/etc.
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However, I will stand up and make a general statement:
A good LED system, using XP-G, and XP-E, with a decent spectrum, should look/grow the same at about 1/2 the power of MH.
And that does match up with what a LOT of others have done of RC and other places.
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BTW:
If power used to heat your tank is a big issue:
1) Insulate. I laugh when I see these open-top, glass, no-insulation, tanks and sumps.
2) Use your gas hot water heater. Run a controlled recirculation loop through your sump.
Need to read them correctly thoughrygh said:
Cree XP-G run in the 110 Lumen/watt range, and that's only the cool white ones, and ONLY if you run them at 350mA, I know quite a few who over drive them to get more light, and the lumen/watt rating drops quite a bit. Halides can get upwards of 115 Lumens/watt, granted that doesn't apply to the bluer bulbs we use, but halides do have that kind of output potential.?? You don't know how to compare, as a result they must be efficient? Yikes man!
I'll make a general statement too, you probably can get away with much less wattage of halides and still get good growth rates than what people normally do as well
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No need to use a hot water heater, I'll run halides and be happy with it
ryanjiang said:
