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I'm lighting a 29 gallon with T8 strip lights using parts cannibalized from a 2 tube and single tube fixture for 3 bulbs total. Not a high light tank but I'd like to maximize what I'm putting into it. It's my first DIY hood and lighting project. I've built the hood, now planning how to arrange the lights

I am purchasing a sheet of spectral aluminum to use as the reflector in the hood. My original plan was to make a ridge on opposite sides (front and back of the hood) and wedge in the sheet of aluminum forming a parabolic arc above/around the lights. Which is still pretty much my plan. However I got to overthinking how I could do this and came up with some options. See bad illustrations:





A. Fill the hood space with a plain parabolic arc
B. Flatten out the top of the arc using a spacer to lower the ceiling, same size sheet of aluminum as A
C. Fill the inside with a larger sheet of aluminum...like b, but with more "space"
D. Use a smaller sheet of aluminum to leave less "headspace" above the bulbs with a plain parabolic arc
E. Flatten out the smaller parabolic arc.

Which, do you think (know) will result in the most light being shown down upon the tank?

On a related note, all my above ideas suppose the three bulbs in line. What if the center one was raised higher or lower that the two outside bulbs? Would that help or hurt light to tank output?

Thanks for your input.
 

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The more space there is between the bulbs the better. Otherwise reflected light just hits the bulbs. Parabolic reflectors are not the best for large bulbs like that, and especially not for 2-3 or more bulbs and one reflector. http://www.ahsupply.com/36-55w.htm has a pretty good sketch of the reflector shape they use, made up of flat surfaces. And, notice that the bulbs are deep in the reflector - ideally you shouldn't be able to see the bulbs without sticking your head right under the light.

If you can get the bulbs far enough apart you can make individual reflectors for each bulb and clip them onto the bulb like is done with T5HO lights.

Or, you could use a "W"shaped reflector behind each bulb, so the light going straight back from the bulb is reflected to the side where it hits the reflector again to be redirected towards the tank. This works pretty well for a two bulb light, with the peak of the "W" in between the bulbs. But, there is no "perfect" reflector for a thick bulb like a T8 bulb.
 

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A good way to figure out how your reflector is to place the bulb where you want it in relation to the reflector. No need to plug it in. Look at the image of the bulb on the reflector. The more of the bulb you see the better. The W-shaped winged reflectors that T5HO bulbs use show 2 distinct bulbs reflected on both sides of the actual builbs. When the bulb is on you see the light from the original bulb + 2 more (from the same bulb being reflected 2 times).

Basically if the bulb is hiding its own reflection from you then the light will be bouncing between the bulb and the reflector.

On a reflector shape like yours (and arch) the bulb will appear smeared and much wider. But you get the idea.

Another thing you could try is to power the bulbs on and manually bend the reflector to where it looks like it's producing the best result.

--Nikolay
 
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