# What to look for in a reflector?



## Noto (Oct 26, 2009)

I want to make some T5 fixtures. I'd like to buy or build efficient reflectors, but I don't really know what makes one reflector design more efficient than another. Can anyone help me out?


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## 61*north (Jun 20, 2010)

The reflector manufacturers refer to their reflectors as "specular" and the word basically means that the product has a mirror like finish... or close to it. That's the most critical piece. In the engineering community a specular finish is referred to as having a high reflectance factor. You want something that's highly specular which will in turn reflect as much light as possible.

The other important component is the geometry of the reflector. You want the shape of the reflector to direct the light back toward the tank and you want as much of that reflected light as possible not to be bounced back at the tube... which would create an inefficient and unnecessarily warm fixture.

To use examples of fixtures I have over tanks:

The tanks that have the regular old cheapo black plastic fixture / lid combo are complete junk.

Next step up in my arsenal is the low profile coralife(sp) fixtures. Not junk. Not much better though as their reflectors are horribly inefficient in spite of the fact that they're highly specular.

The good stuff over my tanks was cobbled together from parts bought mostly from AH Supply. Their lamps are the same stuff you'd get anywhere. Their reflectors though are top drawer. Very efficient and highly reflective. I have no affiliation with their company but have been happy with their product and they offer everything you'd need to build a nice fixture without having to get a second job sporting a shotgun and a ski mask.


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## Seattle_Aquarist (Mar 7, 2008)

Hi Noto,

I have been doing some research on this subject for a 75 gallon project tank I am working on.

For T5 or T5HO I will probably go with TEK2 Reflectors
http://www.reefgeek.com/lighting/T5_Fluorescent/Sunlight_Supply/Tek_Reflectors/Tek_2_T5_Parabolic_Retrofit_Reflector_for_1-54W_Bulb_by_Sunlight_Supply

And if I go with Power Compact/Compact Fluorescent I will go with AH Supply.
http://ahsupply.com/mcart/index.cgi?code=3&cat=9

I chose these reflectors not only for the highly reflective finish but also for the light dispersion characteristic.


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## Noto (Oct 26, 2009)

Thanks, 61*north. Their reflectors are designed for power compacts; would they work as well for linear lamps? I'm considering making the reflectors of plywood or other inexpensive material and then covering them with reflective mylar. Any thoughts on that?

I'm also curious about the specifics of reflector geometry. How do you minimize restrike? How should reflector design change in response to distance to plants, width of tank, etc? For a multi-lamp fixture, is a single curve better than a curve for each lamp?


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## Noto (Oct 26, 2009)

Thanks, Seattle Aquarist. Those look like very nice reflectors, and a good deal.


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## 61*north (Jun 20, 2010)

Noto said:


> Thanks, 61*north. Their reflectors are designed for power compacts; would they work as well for linear lamps?


Generally speaking? Yes. I haven't tried it but my guess is that any loss of efficiency would be imperceptible.



Noto said:


> I'm considering making the reflectors of plywood or other inexpensive material and then covering them with reflective mylar. Any thoughts on that?


I'd pass if you've got a choice, Noto. I'd consider that film to be another (more durable) version of the aluminum foil type of reflector.



Noto said:


> I'm also curious about the specifics of reflector geometry. How do you minimize restrike? How should reflector design change in response to distance to plants, width of tank, etc? For a multi-lamp fixture, is a single curve better than a curve for each lamp?


Restrike is a big issue on HID fixtures. Not an issue in fluorescent to speak of.

The (maybe too) simple answers for your other questions are:

1) Reflector design can change photometrics (the pattern of lit area over the tank) dramatically but generally speaking these are field adjustable in our applications. Just raise the height of the fixture to the point that you're illuminating the tank properly. Lower it if you've got too much light spilling outside the perimeter.

2) A single reflector is generally not better... but once you get to the point of having a highly specular material and a pretty efficient reflector some of these differences won't be easy to spot. (edit: that statement is worded poorly. I should have said that a single lamp and single reflector will be most efficient. In cases where a single lamp has been bent as in a CF lamp... it's still pretty efficient though.)

Personally, if I had to do it over again and had a tank with a 4' length I'd use 4' T5's as they're significantly less expensive in that they're the new office standard. Compact fluorescent lamps are essentially T5's with a U bend in them. You'll note the curiously similar tube diameter when you compare the two. The "T" designation represents the diameter of the fluorescent tube in 1/8" increments, so...

The old style T12 lamps were 1.5" in diameter

The now commonplace T8 lamps are 1" in diameter, and

The new T5 lamps are 5/8" in diameter.

It's easier to build a more efficient reflector for a T5 lamp as the skinnier lamp is easier to miss with your reflected light.


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## Noto (Oct 26, 2009)

Thanks again, 61*north.


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## 61*north (Jun 20, 2010)

Noto said:


> Thanks again, 61*north.


Glad to help, Noto. If you decide to build your own reflector keep in mind that home grown reflector design is a little like playing pool in that tube placement within the reflector will involve the reflective angle, distance to the reflective center, and maybe a little voodoo science if your reflector has any irregularities in it's design.


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## majstor76 (Feb 11, 2010)

Noto said:


> I want to make some T5 fixtures. I'd like to buy or build efficient reflectors, but I don't really know what makes one reflector design more efficient than another. Can anyone help me out?


Check for my reflector

http://www.aquaticplantcentral.com/forumapc/diy-aquarium-projects/71722-my-reflectors.html


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## Noto (Oct 26, 2009)

Thanks, majstor, that's a very clever solution!


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## Diana K (Dec 20, 2007)

A parabolic shape with a notch above the light is probably the best that someone with reasonable skills can make at home. This is for a single bulb. Put the best effort into the reflective surface.

http://forums.tfhmagazine.com/viewtopic.php?f=141&t=27562


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## Noto (Oct 26, 2009)

Thanks, Diana. That looks easy enough. Part of my trouble is that I want my light to be suspended a ways above the tank to allow for taller emergent plants. I think maybe a deeper version of the design you linked to would work (like a hydroponic light design).


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## niko (Jan 28, 2004)

Tek reflectors, individual, for T5HO bulbs.

No need to even look at PowerCompact. That's an obsolete technology that does work, but uses more power, makes more heat, wears off easier. Useful only if you have space constraints.

To make a recessed light the only option is to add "flaps" to the Tek reflector. Or have it inside a deep housing. Also consider where exactly you sit or stand when looking at the tank normally. It may turn out that contaiong the light spill is easier than you thought.

--Nikolay


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## Noto (Oct 26, 2009)

Thanks, Niko. Why Tek, specifically?


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## Seattle_Aquarist (Mar 7, 2008)

Hi Noto,

Good question! Here is a very good discussion on the difference between Tek2 and Icecap SLR reflectors. For a more shallow aquarium I would look at Tek2 and for a deeper tank I would look at SLR.


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## Noto (Oct 26, 2009)

Thanks, that's very helpful!


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## trag (Jan 9, 2008)

As a dedicated Do-It-Yourselfer, I find the pre-made reflectors very frustrating. They cost more per bulb than all the rest of the fixture combined, and I do not think I can reproduce the lovely shapes that they provide. Grrr.

Here's a source for the MIro aluminum which is so reflective: Anomet Reflective Aluminum Specialists. The two materials to look at are the Miro IV and the Miro-Silver, 95% and 98% reflective respectively. However, a 24" X 48" sheet is $45 and $55 respectively and shipping (to the USA) is $120. However, you can get at least four sheets for that shipping and twelve sheets is $168 shipping.

Still, how to bend it without buying an $800 break and shear, and the raw material is about half the cost of just buying a premade reflector.


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## Noto (Oct 26, 2009)

Thanks for the link! It doesn't seem like aluminum should be that hard to bend. I might mess around with some cheap aluminum sheet and see what I can figure out.


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