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Discussion Starter · #1 ·
I have a 8 foot long tank that I would love to light with LED, however i think aesthetically it would need to be a pendant light to make it worth doing with LED, is it possible through use of optics to get enough light and spread to meet high light needs from 3 pendants in a 8' tank? I have seen lots of DIY LED lighting but it seems that often it is more of a light bar arrangement. If I were to attempt this I would probably use some kind of cree 3watt led's I have seen many threads and read lots but nothing specifically on a pendant style
 

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A "pendant" light is just one that hangs over the tank - right? So, an 8 foot long light bar hanging over the tank is also a pendant light. By using the right lenses you can definitely get enough light with LEDs. Cree XM-L LEDs are extremely effective, and not extremely high priced either.

If you want the appearance of 3 individual hanging lights, you could make 3 - 24 inch long lights, and evenly space them above the tank. If you hang them a foot or more above the top of the tank you would get uniform light.
 

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With optics, you have what you have. You can redirect light, but that will cause another spot to be more empty. Diffusing light spreads it, yes, but it also lowers the intensity of the light. If you want strong light, you basically do what Hoppy said and get a few long hanging lights. If you try hanging 3 spot lights you can diffuse it, but the amount of light you lose from that isn't worth the looks of the light. The inside of your tank will be dimmer and anything you try to grow in the tank will need to be much lower light than what you use. I don't think that hanging bar fixtures look bad, honestly, and it would give you much better light.
 

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Discussion Starter · #5 ·
I think if I do a light bar type fixture I will go with tek retrofit t-5, based on cost, unless there is a huge jump in performance with led. How many led's would it take to light a 96x18 area at 24" tall?
 

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Between 24 and 48 XM-L LEDs will light a 96 x 18 area from even further away than 24 inches, 36 inches for sure. If you want to be able to dial the PAR you want to use, LEDs let you do that. If you want to tune the color of the light, LEDs let you do that. If you want to forget about replacing bulbs, LEDs let you do that. But, if you want to spend the least amount of money, LEDs don't let you do that.

If you use 22 LEDs spaced 4 inches apart, with 40 degree optics on each one, 36 inches above the substrate, you should get around 500 micromols of PAR at 750 mAmps. Do 2 rows, one of cool white, one of neutral white, so you can adjust the color, and you can easily get any quality of light you want, from all cool white, to all neutral white, from low light to much too high light. Or reduce the number of LEDs to 18 per row, spaced about 5.5 inches apart, and you get about 200 micromols of PAR at 750 mAmps per row of LEDs. That seems like an optimum number to me, so that's 36 LEDs.
 

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You can also use some PAR38/30 LED incandescent light replacement bulbs and mount them on track lighting strip so you can add or adjust spacing to fill in as needed for coverage.

mulm did a project using this method.
 

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Discussion Starter · #8 ·
I calculated a rough idea of what it might cost from LEDgroupbuy and its not outrageous but its not cheap. $140.00 drivers, $250.00 LEDS, $261.00 heatsinks, $90.00 optics. total is $740.00 would probably turn into $800-850 by the time I built the enclosure system. It is actually not that crazy of a price for the degree of tweakability and energy savings you get. I feel like if I do it I would definitly go 22 on each row just to get the most out of the driver, it would basically cost an extra $100 plus the left over LEDs not used. Is there a better place to buy LED's?
You can also use some PAR38/30 LED incandescent light replacement bulbs and mount them on track lighting strip so you can add or adjust spacing to fill in as needed for coverage.
What are the PAR bulbs like? would it be possible to light this tank with something like that? i assume from a quick search that is like a downlight retrofit with LEDS. Does it just go in a regular mogul socket or does it take something special? since this tank is not terrible deep front to back, I would be curious to try something like that.
 

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I assume you are trying to light a planted tank, so the 6,700K should be good for you. This is an example of PAR value to expect from a PAR38 with 60 degree optics

http://www.flickr.com/photos/[email protected]/6098033653/in/set-72157626054771511

I also mount them on a track with swivel heads.

However, I tend to like MR16 ones more as I can have more control over them using remote controller including dimming.
http://www.flickr.com/photos/[email protected]/5805805342/in/set-72157626179555248
 

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Discussion Starter · #10 ·
So unless I am misunderstanding how many micromoles I need (was still WPG the last time I was involved) it seems like it would take a substantial number of these bulbs to accomplish high light on this tank? What is the ideal # for a relatively high tech co2 tank?
 

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Discussion Starter · #12 ·
found the chart, it is in hoppy's par vs distance thread (FANTASTIC thread BTW) it looks like 80-120 micromoles constitutes high light for a planted tank. I think based on the dimensions of my tank 96x18x24 I would need a lot of the par 38 downlights.
 

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found the chart, it is in hoppy's par vs distance thread (FANTASTIC thread BTW) it looks like 80-120 micromoles constitutes high light for a planted tank. I think based on the dimensions of my tank 96x18x24 I would need a lot of the par 38 downlights.
about 8-10 pcs. of PAR38 at 6" above your tank. Depends on brand, these bulbs are from $70-$90 range. The total isn't that bad comparing to my coral side need. :) We need double the PAR value!
 

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Discussion Starter · #14 ·
Seems like it would put me pretty near the $ range of DIY led hood with controllers and everything. Are you getting good results from these on your reef? From a design standpoint it's hard to shake the pendant halide look but it's just looking less feasible all the time. Its Probably the amano effect (those tanks just look so good) I imagine I am not the first guy who came in here dead set on a pendant set up and gone away shaking his head buying t-5's. What do the ADA tanks run? Like a 400 super high and just not worry were the rest of the light goes?
 

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Seems like it would put me pretty near the $ range of DIY led hood with controllers and everything. Are you getting good results from these on your reef? From a design standpoint it's hard to shake the pendant halide look but it's just looking less feasible all the time. Its Probably the amano effect (those tanks just look so good) I imagine I am not the first guy who came in here dead set on a pendant set up and gone away shaking his head buying t-5's. What do the ADA tanks run? Like a 400 super high and just not worry were the rest of the light goes?
The magic is they added color to their MH. I simulated the same with my friends' planted tank. Not perfect at the time but very close. LOL. To do that, the bulb cannot be just any PAR38, it has to be mixed color as well.

If my camera can pick up the color, I will try to shoot a pic of my discus tank where I am getting close to Amano MH look in color even though i did not try to simulate the intensity. You know discus don't like too strong light.


BTW, the good PAR38 will give you the shimmer effects similar to the MH.
 

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Don't try to use high light! I think it is well proven now that the biggest effect from using high light is the huge increase in work required to keep the tank algae free and looking good. Using high light means you have to get the CO2 just right, with great in-tank water circulation, very good water surface ripple, and any other thing you can do to keep the level of dissolved oxygen in the water as high as possible. Plus, the plants will need pruning very often or it soon becomes clogged with excessive plant mass.

If you stick to 40-50 micromols of PAR, and use pressurized CO2, you can still grow the same plants, grow them very well, but have slow enough growth rates to not have to prune nearly as often, plus having algae far less likely to start growing.

That will drop the price of the light you need, substantially.
 

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Discussion Starter · #17 ·
I like it, 40-50 micromoles is a pretty easy/cost effective # to hit. Would I be able to grow a low carpet of hc or glosso with this amount of light? I have not totally decided on an aquascape yet but I am leaning towards an iwogumi type layout using large stones and a carpeting plant.
 

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Don't forget, it might cost more for a LED fixture, but doing quick math, at the photo-periods we use it is something like 10 years of use before the LEDs loose 25% of their power being driven at max (maybe longer under full drive). Add up the cost of replacement T5 bulbs or ballasts etc, and for my upcoming SW build I found out I would pay the differance in DIY LED to off the shelf T5 in less than 2 years.
Add to that less tank heating, color blending, etc, it is the way to go.

In other words, DO IT lol
 

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$75.90 ALT 20 Watt PAR38 Dimmable LED Light Bulbs
Brand: ALT
Part No.: LL-PAR38-D-20-ALT-W/WW
Wattage: 20 Watt
Voltage: 110 Volt
Base Type: E26
Standard Beam Angle: 60°
Compare To: 125W Halogen
Length: 6.3 in.
Face: 4.9 in.
Life Hours: 50,000
Light Source: Bridgelux LED
Warranty: 5 Years
Case Quantity: 6
True Dimmable
Color: White
Color Temp. (Kelvin) 6000K
Lumens (Initial) 1320


$112.90 Eterna Bright 36 Watt Dimmable PAR38 LED Light Bulb
Brand: Eterna Bright
Part No.: LL-PAR38-D-CREE36 W/WW
Wattage: 36 Watt
Voltage: 120V AC
Base Type: E27
Standard Beam Angle: 60°
Aluminum Fin Cooling
Compare To: 100+W Halogen/Incandescent
Body Length: 4.75 in.
Face Width: 4.75 in.
Life Hours: 50,000
Light Source: Cree LED
Warranty: 5 Years
Case Quantity: 12
True Dimmable
Color: White
Color Temp. (Kelvin) 5300K
Lumens (Initial) 1415
 
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