Led Lighting - Spectrum Question

[macrosloth]

I've built a few things before and am okay with the basics of working with LEDs, but I am wondering how to choose what Kelvin LEDs to use for optimal plant growth. Some people seem to use a mix of red + green + blue in addition to the whites. Is this just for looks to make colors of fish and plants brighter?

Additionally how do you size your LED lighting, is there recommendation lumens/gallon?

I used to aim for 2-4 watts for t5's and wikipedia says 54 watt T5's are around 5000 lumens.. I realize that a lot of light from a T5 never reaches the tank where leds are more direct in their beam..

Thinking of using CREE XML's and driving them around 3 amps (about 10 watts)... A lot of the larger Leds 25-100 watts don't seem to have the same efficiency and generate a lot more heat.. SST-90s are cool, but way to much $$$... Running 1-3 watt leds seems like a PITA as you need so many in a string..

[someguy]

i don't have the technical knowledge as you, but i do have some experience with the standard marineland built LED's. On my 90'g i have 1x48" 2x24" marineland double bright's, plus 2 x t-5. It's a heavily planted, non CO2 tank. LED only plants live, and grow. But tank is left looking slightly washed out. Adding the T-5's, fills out the apperance, and plants thrive.

So, if it was me, and i wasparting the together, i'd go for a 80/10/10 mix. *0%white, and 10% blue and red. I would expect that to be relatively close.

Side note. At King ED`s, over one of their discus tanks, they had some kind of LED light that had an equal mix of red blue and white, and it left it looking kinda funny. Also, the LED did not have any kind of lens, and that seemed to make odd reflections on the top of the water, and various reflection points, very distracting.

[verkion]

Have a look at my DIY that I did for my 29G Biocube. I'm still running only 4 of the LEDs (didn't retrofit the 5th in as I was planning) and it is plenty bright. 6500K spectrum 20W LEDs that put out maybe 1500 or so lumens a piece. And it was cheap. Everything from Dealextreme.

[tang daddy]

I can't say I am a pro at LEDs but my friend and I put together a couple DIY fixtures consisting of 56 led of 3w crees over a 75g tank. Please keep in mind that my tank is also a reef tank and needs more light than a planted tank.

Edit: I answered my own question upon looking up XML crees on google, you could drive them up to 3a or as low as 300ma. These probally put out a ton of light and heat!

I have mine at 700ma for both the cool whites and royal blue, the cool whites can run up to 1.4a but they suggest running them lower to prolong the life of the led. I also have my set up on dimmable drivers at 65% currently nd they put out no heat, I really don't need to run fans but since it's all wired have run the fans anyways.

I may have misread but how big of a tank are these LEDs going on?

I would suggest you run the LEDs with no lense aswel because if you use lenses it greatly focuses the light and causes spot lighting.

My LEDs are spaced 1.5" apart on 2 10"x14" heatsinks and seem to have a good spread over a 48"x18" foot print.