Alright, I lied. But at least I found what I was looking for!

Looks like 70 degree optics make the most of your LEDs:


Source

However, reading through this again, they didn't test the 40 degree. My assumption is that this source is trying to show you how to get the most par using the least LEDs. Take it with a grain of salt, I'm no expert :)

Here is an interesting read on optics in a tank

http://www.nano-reef.com/forums/inde...owtopic=261525

what would be optimal for a diy fluval edge, in regards to optics, as the canopy forces them to be kept very close to the surface.

With the Edge you don't want to use optics as the opening is so small, you want the light to scatter as much as it can When I get a chance I will upload a couple pics of the DIY LED lighting for my edge.

k cool!

It is interesting read .What is best height to hang if you using 70 deg optic for DIY fixture

Here's a good link:

http://www.ledgroupbuy.com/pages/Cho...ght-optic.html

But it also depends on how deep your tank is. The higher you go, the wider the spread, but the less penetration you'll get at the bottom of your tank.

But with a wider optic like 70*, you can afford to go lower, as the spread is already wider. Just think of a flashlight. Take one and hold it vertically, pointing down, and see how the spread is.

Realistically, I would hang the fixture as low as possible, while still giving you enough clearance to reach your arm into the tank to do daily maintenance.

That link is very good,thanks.

28LED Build -- Done
 

The LEDs game last friday, so I spent the evening gluing them onto the fixture and wiring everything up!

DIY Aluminum Fixture:
http://reefblog604.files.wordpress.c...2325.jpg?w=530
I used 2 of the left piece side by side for the main body, and I interlocked and riveted in all 4 sides with the right piece.

Top View:
http://reefblog604.files.wordpress.c...4300.jpg?w=530

Bottom View:
http://reefblog604.files.wordpress.c...4336.jpg?w=530

Side View:
http://reefblog604.files.wordpress.c...4405.jpg?w=530

LEDs:
http://reefblog604.files.wordpress.c...1446.jpg?w=530
http://reefblog604.files.wordpress.c...1528.jpg?w=530
I was going to install a piece of plastic on the bottom as a splash guard, but I havent gotten around to getting the plastic. But now I'm wondering if it's even necessary. I'll probably hold out.

Grommets for running wires through:
http://reefblog604.files.wordpress.c...1733.jpg?w=530

Wired up (48" strip of blue LEDs as Moonlights wrapped around fixture):
http://reefblog604.files.wordpress.c...1747.jpg?w=530
http://reefblog604.files.wordpress.c...1759.jpg?w=530

Temp electrical station :P
http://reefblog604.files.wordpress.c...1805.jpg?w=530

Top view with fans (80mm Aluminum fans with blue LEDs, fitting):
http://reefblog604.files.wordpress.c...1848.jpg?w=530

Front View:
http://reefblog604.files.wordpress.c...1843.jpg?w=530

Fixture runs COOL TO THE TOUCH on full load. Blues at 800mA, Cool Whites at somewhere over 1000mA. One of my goals was to demystify the belief that you need those honking 20lbs+ Amplifier style heatsinks. Pretty cool that ALL the parts of the fixture are aluminum, from the body to the rivets, and even the 2 fans and the screws are Aluminum. I'm very happy with this LIGHT WEIGHT fixture.

I had made the 8LED Fixture, and now this. It's been really good practice. This second one took me no time at all. It's all about the planning. However, I did not anticipate building this 28LED fixture, so the big fixture for my display tank has been pushed back to next year. I just got a new order of bulbs, so they should hold me over until the next LED build (I'm thinking around 60 LEDs next year).

Nice job!! that looks fantastic. People never believe me when I tell them they can use U-Channel for their heatsink.

Keep an eye on the frags at the top of the tank,t hey might bleach with all the new light.