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post #3 of (permalink) Old 01-20-2013, 04:34 PM
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Join Date: Dec 2005
Location: Sacramento, CA
Posts: 21,015
Originally Posted by unicknn View Post
Im in the process of planning out a planted tank. Ive had lots of tanks in the past and have always wanted to try a planted tank, I scored a free 45 gallon bow front today so its starting soon.

Im having some issues with figuring out the needed lighting.

Im planning on going for around 70 PAR( I thought I read this was medium, now its looking like this is high, can someone clarify?),
In my opinion you should treat 70 PAR as high light, so good CO2 is essential.
this is a good start in a medium light, I want to start the tank without CO2 and then later on add it as I add more power to the lighting system... if I decide too.

Im using Hoppy's Excell and this is what Im finding:

LED spacing 2.25
PAR 70
rows 3
height 24"
cone angle 60

This shows that I can use Cree XP-E-Q5 LEDs at half power to get where Im looking to go.

My questions are this

1) the LEDs say their angles are around 125. Do I need to use LED lenses to get the desired 60 degree angle?
Yes, you do need 60 degree optics to get the 60 degree beam angle.

2) how far should the rows be spaced?
The row spacing should be about the same as the LED spacing, so 2-3 inches should work fine.

3) how long should these rows be? My tank is about 3 feet long. Im assuming that the strips should be as long as the tank.
If the rows are as long as the tank you get a lot of light spilled over the ends of the tank. If you make the rows much shorter, the PAR drops quite at bit at the ends of the tank, even though reflected light off the end glass does increase the PAR some. You can make the rows be almost as much shorter than the tank as the space from the rows to the front and back glass, or just make the rows about 2 LEDs short on each end.

Am I on the right track? I know Ive got alot more reading to do but these will clear up alot of confusion for me.

I think you are on the right track, but be sure to use a dimmable LED driver, because that calculator can't be assumed to give an exact prediction of PAR, and, for the same reason, design based on the maximum PAR you think you might want.

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