What's more reflective? DIY lights - The Planted Tank Forum
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post #1 of 26 (permalink) Old 01-16-2012, 04:48 AM Thread Starter
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What's more reflective? DIY lights

So I took out the "guts" of a standard strip light, screwed a couple holes in the back for wiring and such, and turned a 30inch tube fixture into a 4 CFL bulb fixture. Went from like 20 watts to 92 watts (4x23w bulbs). Worth taking the 30 mins to build? Hell yea!

The questions is...what would be more reflective to help get all the light from those 4 bulbs into my tank? I just see other peoples tanks with 2-3wpg and I'm like...IT'S SO BRIGHT! Then I look at mine and although it is well lit, I feel like there has got to be some reflection problems because it doesnt look like 92 watts is hanging over my (30 gal) tank. Right now I have tinfoil taped directed under/over the bulbs on the inside of the fixture, but I was wondering if white spray paint would give me better results?

Throw in your 2 cents. If you want details on how I made the fixture just shoot me a PM or if I get enough results I'll just make a new thread.
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post #2 of 26 (permalink) Old 01-16-2012, 12:44 PM
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Hi. It would be helpful if you upload a pic or two of your project.

I went that route in 2009 (I posted about it with pics in another forum). The simple answer would be: get the brightest white spray paint you can find and paint the interior of the housing fixture. I got that from reading a lot of what was posted on the subject. Hoppy made some PAR measurements and found insignificant differences between bright white painted and millar reflectors (both were DIY I think).

That said I had heat issues with CFLs. There's a fire hazard due to melting plastic so be careful. I ran several CFLs in a DIY PVC (graded for high pressure) fixture and the 23 and 22W left a pretty dark burning mark. I melted a Perfecto light fixture plastic housing with 22W CFL fortunately I was there when it happened and I still remember the smell of melting plastic.

Thing is CFLs re-strike too much and end losing their output quite fast for photosynthetic purposes. I did the math back then and for a short term solution it makes sense (say 1 or 2 months); as for mid term I ended having a lighting fixture that went from high light to low light in a matter of 6 to 8 weeks (I ran 12 to 14 hours photoperiods back then).

Too much light usually ends being more of a problem than a solution.

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post #3 of 26 (permalink) Old 01-16-2012, 01:36 PM
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Originally Posted by pepetj View Post

Thing is CFLs re-strike too much and end losing their output quite fast for photosynthetic purposes. I did the math back then and for a short term solution it makes sense (say 1 or 2 months); as for mid term I ended having a lighting fixture that went from high light to low light in a matter of 6 to 8 weeks (I ran 12 to 14 hours photoperiods back then).
Thats not an issue with re-strike, thats an issue with improper cooling. Take a look at a CFL bulb, almost all of them say "not for use in enclosed fixtures".


They need to either be out in the open, or be actively cooled.
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post #4 of 26 (permalink) Old 01-16-2012, 02:15 PM
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I have been told that white paint would be more reflective.
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post #5 of 26 (permalink) Old 01-16-2012, 06:31 PM Thread Starter
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Pepetj- Thanks for the info. To solve the heat problem I drilled small vent holes in the top and back of the fixture. It does get hot, but not hot enough to melt the housing.

Rich- I think there should be enough air flow through the fixture since it's elevated off the glass a few inches. Any hot air trapped inside the fixture would make it's way out of the vent holes in the top.

Touch of sky- I've heard white paint would be more reflective as well, just wanted to get other people's insight. I don't know whether it would be worth it to buy a can of spraypaint to even find out. I would imagine I need to get the Krylon stuff so it's safe for the aquarium. I don't plan on dipping the light fixture in the aquarium, I'm just being prepared in case the paint chips haha
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post #6 of 26 (permalink) Old 01-16-2012, 06:54 PM
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I wonder about mirror chrome paint?
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post #7 of 26 (permalink) Old 01-16-2012, 07:01 PM
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I've read white paint is better than those options when you are dealing with a flat surface and not a well designed single bulb reflector.

For DIY enclosed hoods I've always used a two part epoxy paint made for painting old bathtubs.
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post #8 of 26 (permalink) Old 01-16-2012, 07:41 PM
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White paint, preferably flat, reflects the most light for any kind of reflector with a non-optimized shape. Just ask any grower of a certain illicit plant. Though I'm not one, there's plenty of knowledge that carries over to our hobby.

That said, sometimes it's beneficial to use aluminum foil or tape. Heat rises, and even in a plastic hood with plenty of ventilation holes, it may eventually melt or warp the plastic directly over bulbs. I know I'm not the only one who's melted an incandescent hood by putting in CFL's, then removing the aluminum reflectors to make a little extra room for the larger bulbs. Those reflectors aren't just reflectors, they also keep heat from rising straight to the plastic, and spread it out like a heat sink.
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post #9 of 26 (permalink) Old 01-16-2012, 08:37 PM Thread Starter
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Appreciate the input everyone! Wish I had this many replies on my racking system
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post #10 of 26 (permalink) Old 01-17-2012, 02:04 AM
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I have made simple sheet aluminum reflectors shaped like \_/ to fit over each CFL bulb, and it doubled the PAR readings from those bulbs. I used what was probably intended to be flashing material. I bent it with a couple of boards clamped on the aluminum with a 3rd board used to spread out my hammering when bending it. Then, I adjusted the angles by hand until I could see a fuzzy image of the bulb on each side of the bulb. I didn't do much polishing of the aluminum either.

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post #11 of 26 (permalink) Old 01-17-2012, 09:21 AM
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Quote:
Originally Posted by Hoppy View Post
I have made simple sheet aluminum reflectors shaped like \_/ to fit over each CFL bulb, and it doubled the PAR readings from those bulbs. I used what was probably intended to be flashing material. I bent it with a couple of boards clamped on the aluminum with a 3rd board used to spread out my hammering when bending it. Then, I adjusted the angles by hand until I could see a fuzzy image of the bulb on each side of the bulb. I didn't do much polishing of the aluminum either.
So I've been reading about how reflectors really effect your light out put by thei material and shape. But I never knew the angle of the reflector is the most important thing... Could you elaborate more on what angle and shape is the best for the maximum reflection of the light.

i.e. my light fixture's reflector (one piece) are not even folded but much more like a bent shape like a dome sitting on top of two t5ho's... So I'm assuming mine is not good?


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post #12 of 26 (permalink) Old 01-17-2012, 03:16 PM
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So I've been reading about how reflectors really effect your light out put by thei material and shape. But I never knew the angle of the reflector is the most important thing... Could you elaborate more on what angle and shape is the best for the maximum reflection of the light.

i.e. my light fixture's reflector (one piece) are not even folded but much more like a bent shape like a dome sitting on top of two t5ho's... So I'm assuming mine is not good?
Think of it like playing pool or snooker.

Light will bounce off a surface at an identical angle to where it originated from.

If the mirror surface is vertical adjacent to the bulb, light is going to bounce back to the bulb horizontally.

A dome or parabolic reflector is typically very good but they are best at focusing light in a specific place - but that's not to say that yours does that - its so easy to change how a reflector redirects light just by adjusting how shallow or deep the reflector is.

Your reflector is probably just fine.
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post #13 of 26 (permalink) Old 01-17-2012, 04:14 PM
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The simplest possible way to adjust the angles is to look at the bulb, with the reflector in place, and see if you can see a complete reflection of the bulb on each side of the bulb, so you seem to have 3 bulbs, not just one. If you get that, you have the best angle on the reflector. You can use two bends on each side and with great care get two reflections on each side of the bulb, but then the reflections are usually just partial bulb reflections, making adjusting it much harder to do.

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post #14 of 26 (permalink) Old 01-17-2012, 05:50 PM
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Go to home depot,,in the heating section,,there is foil ductwork tape,,very reflective and self sticks too..just be aware of any direct heat from the bulbs..
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post #15 of 26 (permalink) Old 01-17-2012, 07:37 PM
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Go to home depot,,in the heating section,,there is foil ductwork tape,,very reflective and self sticks too..just be aware of any direct heat from the bulbs..
+1 on that Jone . . . when I made my prototype fixture, I built it out of plywood and lined the inside with that foil tape. IMHO tape is better than paint:
~there isn't any solvent to cook off and stink up the house
~It's immediatly ready for use after application (doesn't need to dry)
~It is rated for 120+ deg F and won't fade / break down from long term light exposure.

After my plywood/foil tape proof of concept, I built the actual fixture from 5052 aluminum.

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