[Tex Gal]

Hoppy this is so interesting. I was under the impression that aluminum foil was NOT good, which is why everyone was looking for mylar.

I have a 10g hood that is similar to yours except that the light opening is much larger. It had two small dull aluminum reflector with black plastic surround. Just 2 nights ago I used the spray adhesive and glued 3ml mylar into the hood. I overran the mylar to most of the black plastic around the light area. Visually there seem to be a lot more light in the tank. My plants had been doing well since I switched to the spiral fluorescent bulbs. I am anxious to see if they do better with the mylar.

 

[hoppycalif]

I know I was certain that the mylar was far superior to aluminum foil. I spent a lot of time trying to get some back when I was making a light fixture for a 29 gallon tank, about 5 years ago, and again when I did this 10 gallon fixture modification. It is embarrassing to be so wrong!

 

[aquaphish]

Today I looked at this fixture and hood more closely. The original Perfecto hood and fixture has glass between the light and the water, mounted on a lip in the hood. The lip is about .38 inch wide all around the opening for the light to go through. The opening is 3 inches by 18.25 inches, so the lip reduces that opening by about 30% in area. That is acting as an aperture to reduce the light entering the tank. So, I trimmed the lip out with a utility knife.

I did some measuring of the light from the fixtue, using a PAR meter, and charted the results:

The red dashed line is what I should get if I replace the mylar reflector material with plain aluminum foil. And, that would, in total, represent a major improvement in the amount of light this fixture provides at the substrate level.

What is the actual PAR reading after the Mylar was replaced with aluminum foil?? Just curious.

Reading from the begining and seeing your setup, reflectors would seem to not be effecient enough to really improve your lighting.

By making a reflector the full lenght of the hood will be better. This will give you full reflection of all available light in the hood. Just placing a reflector behind the light and no other place you are not really reflecting all the light that the bulb is displacing.

Also having a rounded reflector also impeds the reflection of available light. The light will bounce back into the light instead of reflecting into the water column. What needs to be done is to have angles that will better reflect light into the water.

I really think the bulB is also too close to the reflector cutting down the reflected light. What is happenig is when the reflector is too close to the light and you have such a large light the relfected light is being blocked by the bulb.

My final suggestion is to, if you can, move the light further way from the reflector and also make a sheet metal forming fixture with beveled angles to form angles on the reflector. This will give you the ability of reflecting the light away from the bulb and into the water.

The forming tool will be used by placing the sheet metal on the fixture and holding it down with a clamp. Then go at it with a hard rubber mallet forming the sheet metal around the wood forming tool and making sure you have good sharp corners at the angles.

Enough I think I can write a book here on this subject.

Also one last thing, you did the light testing out of the water. What are the results when you test with the probe submersed, if you can submerse it. This is the real test that should be done. Light is reflected out of the water at the surface of the water unless it is at a certain angle,where the light penetrates the water, which I don't remember right now.

THE END!!!​

 

[hoppycalif]

Not quite "the end"! Look at http://www.ps.missouri.edu/rickspage/refract/refraction.html, and play with the graphic calculator there. You will see that most light hitting the surface of the water is refracted into the water, not reflected. There is, of course, more to it than that simple calculator shows - some of the light is reflected at almost all angles, but as I recall, it isn't a lot. For example, I can't remember seeing a sun reflection off the water that was anywhere near as bright as the sun.

About the reflector size, location and shape: The location is limited to what can be fitted into the fixture, and I placed mine as far away from the bulbs as I could. If I were to build a fixture I would certainly allow more room. The size of the reflectors has to be such that the reflected light enters the tank - it does no good to reflect light into the ends of the fixture. If I were to do this with white painted reflectors I would use a full length reflector, because some of the diffuse reflection, even at a distance from the bulb, would still make it into the aquarium. The shape of a reflector for a complex shaped bulb like the screw-in spiral bulbs is almost irrelevant. There can't be a perfect shape for such a shape and size source of light. I tested my reflectors by just looking at the reflections from the angles of interest to me. They do reflect a full image of the bulb at those angles, so the shape is about as good as I could get. But, again, with white painted reflectors a different shape would have been better, and even with aluminum foil, with crinkles, would do better with a different shape, I think. Working with screw-in CFL bulbs is like getting blood out of a turnip - there just isn't that much to get.

I tried to use the PAR meter sensor in the tank, but it was futile. There just isn't room to reach down into the water under the fixture, hold the fixture in a specific location, pointed in the right direction. I gave that up when I found I could get just about any reading I wanted to see just by slightly twitching my fingers, and I never could be sure exactly where the sensor was located under the light. Doing that part right would require much more elaborate fixtures than I wanted to try to make. What I did convince myself of was that the readings were in the same ballpark under water. From then on I concentrated on comparisons with a known good light - my AHS fixture, in the air.

 

[HockiumGuru]

alot of great information here.

any conclusions as of yet?
Is the white plastic reflectors better, or aluminum foil?
Also, You must have had some huge lips on the canopy of your tank to be limiting 30% of possible light. I haven't looked to closely at mine since reading that, however I don't believe the lip on my 10g is that large

 

[hoppycalif]

The lip that was blocking light was only .38 inch wide, but if you take the 3 inch by 18.25 inch opening - 54.75 square inches, and increase it by .38 inch all around, it becomes 3.75 inch by 19 inch - 71.25 square inches. 54.75 divided by 71.25 is .77, so I actually had 23% blockage of the light. (not 30%) By cutting out that lip I increased the area by 30%.

I don't know if white plastic is as good as white paint, but it isn't likely that it is. A lot of things look white, but are really a light gray, and I think white plastic is one of those things. Good bright white paint is a very good reflector, which is what makes it look so white. But, it appears that aluminum foil is slightly better than white paint for light at the substrate level. The difference isn't big, but it is measurable. If I were to replace the little reflectors with a full length one, painted white, I suspect that would give at least as high an intensity at the substrate as the aluminum foil does.

Incidentally, I have covered the reflectors in that 10 gallon tank fixture with aluminum foil now, and the improvement is about as I predicted at the small distance from the bulbs, but not as good as I predicted at the substrate level.

 

[ghengis]

OK, I've now read this Thread about 17 times and decided to rip the guts outta my 11w "light". I'm dead keen to give this mod a go (sourced globes sockets at the local hardware), but I'm a little nervous with wiring this up. Can someone provide a wiring diagram to go from one cable to a split into two? How do I ground it? How do I know whether I need a ballast?? I'm not unfamiliar with DIY, and I'm actually pretty handy when it comes to tools and fixing or building things...just not alot of experience with electrical fittings.

 

[hoppycalif]

Here is a simple diagram of how this should be wired: Remember, these powersaver CFL bulbs have their own built-in ballasts in the base of the bulbs, so no ballast is needed.

 

[mulita]

..
Incidentally, I have covered the reflectors in that 10 gallon tank fixture with aluminum foil now, and the improvement is about as I predicted at the small distance from the bulbs, but not as good as I predicted at the substrate level.

hoppy:
By aluminum foil, you mean the regular household aluminum foil used in the kitchen or what is it? I just read the whole thread as I will be working in reflectors for my project using CFL Bulbs and I was thinking to use White Pre painted Aluminum sheets as reflectors, I have access to a brake press so I was thinking to do similar angles as AH has in their reflectors, but now reading about the aluminum foil just light up curiosity on me about if that could be a better choise instead.

 

[hoppycalif]

Regular household aluminum foil is all that I used. It is a high quality material, even if it is cheap. I'm still not sure if aluminum foil or very good white paint is the best reflector for most lights. A lot more testing would be needed to determine that to my satisfaction, and I haven't had the time to do that.

 

[ghengis]

Nice diagram, hoppy. Cheers. The lead on my fitting is a two-pin/two-wire arangement, so I guess I'll just ignore the green wire in the diagram. Also, the housing is only plastic, so no problems with metal shorting out there. Just need to get imaginative with mounting the sockets, and Bob's yer Aunty's live in lover...

 

[mulita]

Regular household aluminum foil is all that I used. It is a high quality material, even if it is cheap. I'm still not sure if aluminum foil or very good white paint is the best reflector for most lights. A lot more testing would be needed to determine that to my satisfaction, and I haven't had the time to do that.

OK. So I guess if I am going to do the pre painted Alumimum will be worth to try it like that first and checkout, unfortunately a meter is needed to be sure.

 

[hoppycalif]

OK. So I guess if I am going to do the pre painted Alumimum will be worth to try it like that first and checkout, unfortunately a meter is needed to be sure.

Not a bad approach, but remember, not all white paint is really white. Pure white painted materials are almost painful to look at, they are so bright. I think paints called "ultra white" or something like that are likely to be the purest white you can get.

I doubt that anything you purchase that is already white is really very white. I could be wrong about that though.

 

[grim]

Sherwin Williams can mix there own paint home depot and Lowe's should be able to but i never use them i have found that even the whitest paint on the market if you have them add two ounces of white it makes it more pure since paint is 98 percent water

 

[mulita]

I just built the reflector I was getting advise from Hoppy here. I show up this in another post but here are the picture to share.

Reflector

 

[Aquaticz]

whaaaaaaaaaaaaaaaaaaaaaaa
no pics
makes this one a bit useless

 

[ashaf22789]

Well keep in mind it has been almost 3 years since the last post.

 

[k zeller]

The original pics dont work anymore.