Backyard Aquaponics
A place to discuss aquaponics

Hi DF:

I am using a 400 watt MH over about 4x4 grow bed area, with foil-faced insulation to make the light bounce around. The heat helps warm the water, which is good for the tilapia that are in the system. I have grown a lot of lettuce, and basil. A coupld tomatoes are growing in there now but they get very big for the small space, and I have green pepper plant that has over 6 peppers on it right now. The light can be switched to a sodium bulb to encourage fruiting. I got the light from a hydroponics shop on eBay for about $200 (included $40 for shipping because the ballasts are heavy) and it came with a lighter!

Thanx VB...........i WANT to believe!

Good info.

i wonder how many watts per fitting.............might even be worth it.

thank you DD, i wonder what they want you to use the lighter for, lol.

I know chilli plants will grow to about 9" high in february quite happily with just a single 20w compact florescent for light.
The problems start when they get bigger..so choosing low height plants would be a good plan, cherry toms with a mainly horizontal growth habit might be quite economical to illuminate.

Wouldn't the leds have a narrow spot of light as opposed to full coverage?

I was unsure where to put this so decided to resurect this thread.

There has been some debate over efficiencies of lights.
Page 43 of the How to Hydroponics PDF has a very clear and easy to understand chart of the chlorophyll activity of plants at various K's. And an explanation of the effects of colour (temp) on plant response on the previous page.

was there a link somewhere?

Steve link http://www.mod-home.com/downloads/HowToHydroponics.pdf

Courtesy of dandman and jazzplayer

Yes, thats a pretty good primer for hydroponics. When I see the rubbermade totes I think, how many fish would fit in there...

I read somewhere on the net about a guy who was growing with LED lights -- blue and red. His argument was that only narrow portions of the light spectrum is actually used by the plants -- so give them exactly the wavelengths they need and nothing else.

The pictures he posted were erie but the (pot) plants seemed to be thriving. Not sure why most of the cutting edge horticultural research posted on the net is related to relatives of the hemp plant.

If that works, that would be a great energy saver. 2 watts for LED vs. 400 for HPS.

Just found this: http://www.ledgrowlights.com/sales_retail.htm

Looks nice, kinda pricey though.



Ah! ebay to the resuce!

The costs for LEDs won't add up for awhile, compared to conventional HID bulbs. You could get 3600 watts, 9 400 watt MH/HPS ($200 from eBay might be found cheaper too) for the cost they're asking for the 240 watt/1000 watt equivalent LED setup there.

Hydroponics PDF is great! Thanks for posting it Sleepe!

Yes, research show that its a couple narrow bands of light. I was reading that from a university website.. cant remember where now.. I think two colors will work, but a third is even better.. A setup to run directly from the line power would require about 41 leds. Looks like they used two sets in each light? Anyway... It would be super easy to layout a pcb to mount LEDs to. The question is what are the colors needed? More specific than red and blue. Once I can find a suitable LED color then I can price such a thing.. If they are about $1 per LED then it would be possible to make them for half what they are selling them for. If you buy 1000 LEDS then its only $70.. To me that would be worth the effort.. PCBs could be mass produced pretty cheap. The fun part is soldering in 80+ LEDSs..

A pot head site has some compared photos using LED vs MH lights..
Here

The hydroponics pdf has the chlorophyll spectrum graph in it, you can see the two bands that are significant.

Ok for the photosynthesis 680 nanometers is ideal and phototropic responses are idea in the range of 440 to 480 nanometers. The suggested ratio is 1:4, Blue:Red.

Here are the charts using wavelength instead of light temp; which is how you order you L.E.D.'s


And for reference:


So anyway 1 Watt LEDs seem pretty cost effective at $2.39 for 1 watt vs over $7 for 10 100mW LEDs.. 465nm 1Watt cost $2.69 and a 624nm 1 watt is $2.22..

Because you are not wasting energy making light plants dont use then this is efficient. So it would cost $233 for 100 watts of L.E.D. Growing light..