2000 Lumens - Low Med or High?

[woofwoofgrrl]

It would be from 6 LED's spread across the 36 inch length of my 30G long tank. Would that be considered Low- Med- or High light? Or does it depend on how long I keep them on each day?

Thanks!

 

[fort384]

photoperiod does matter... what kind of LEDs are they?

 

[woofwoofgrrl]

They are the Bridgelux LS Series
http://www.bridgelux.com/assets/files/Bridgelux_LS_Array_Data_Sheet_01-26-10.pdf
I was going to go with 3 Warm White and 3 Cool White to get good peaks at both of the critical spectrum ranges.

 

[fort384]

ok cool. I will preface this with I have not done LED lighting on top of a planted tank... but here is what I would say based on what I have read, and what other forum members are doing/have done:

You could grow medium high or even some high light plants with these lights at full power. Consider adding a potentiometer to the build so you can dial in the appropriate amount of light, depending on whether you plan to dose ferts and add CO2 injection.

http://www.aquariumadvice.com/forums/f20/high-power-led-fixture-for-a-planted-tank-141021.html

There is a lot of good info in that thread about a DIY build. You may find it useful... I am sure he wouldn't mind you asking some questions there as well.

 

[BigJim]

Personally I would go with more lower-power LEDs. I don't think you would get good coverage with only six LEDs. You'd get a spot light effect. You can probably grow high-light plants directly under the LED, but the light power will taper off as you move away from the center.

Do you have a specific model of LED in mind? There's a lot of variance in that LED series.

 

[woofwoofgrrl]

Gah! This this the third time I've written this, I keep hitting the wrong key and blitzing what I've written.

I'm leaning towards the BXRA-W0260 and BXRA-W0360's. They have a 120 degree viewing angle. I'd agree with you if they were the old fashioned LED's with a narrow viewing angle. If I'm interpreting page 12 of the datasheet correctly, only the top 3 inches at the very front and back of my tank will have less than 75% intensity. I also did a coverage chart with the LED's 5.5 inches apart and it looks pretty good - lots of overlap at 20 degrees/95% intensity.

 

[woofwoofgrrl]

Okay now it submitted before I was done....at least I didn't lose it this time!

Anyway..... the best thing about being DIY, is that if I've completely screwed up my calculations, I can always change things!

I like the potentiometer idea! They will also be switched individually off the DC bus. I don't want to rush into figuring out CO2 and ferts since I'm still figuring out the basics, so the ability to control the light level is a good idea.

I checked out your build thread BigJim - very nice!

 

[BigJim]

It sounds like you did more research and planning than I did for my fixture. I didn't lay out any coverage diagrams. I believe my LEDs are 4" apart and they have a 90 degree viewing angle. I spaced them relatively closely in case I had to use optics to focus the light a bit. It's looking like I overbuilt the fixture for a FW planted tank at the moment.

The potentiometer dimming has been a lifesaver for me. I decided at the last second to add the dimmer based on instructions I found on the web page where I bought the driver. I've been running the tank at 1/2 - 2/3 brightness because I had GSA on the glass after one day of full-power lighting with no CO2 and only Flourish for fertilizer.

Instead of switching the LEDs, you could use transistors and a pot. I'm hoping to eventually go the transistor route and add some IC control for sunrise/sunset and moon phase effects.