hoppycalif

My plants are not doing well. The actual light intensity at the substrate level seems to be too low, but I'm still experimenting to try to figure out if that is the reason. The tank now has glosso and rotalas in it, plus a small crypt.

If I had that bulb over my tank I would try to figure out how to get a mylar covered aluminum reflector in there to try to get more out of the bulb. I suspect that a tubular light like you have may suffer less drop in intensity with depth than I get with the CFL bulbs, so your 14 watts may give more intensity than my two 20 watt bulbs, down at the substrate.

 

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hoppycalif

If I can think of an easy way to get a white reflector in there without ruining what I now have I will make some measurements with it also. I doubt that I will try the aluminum foil though. I can probably keep the PAR meter for a week or so.

jazzlvr123

i diddn't read the whole thread so it might be stated already but did the mylar not workout?

hoppycalif

Under the lighting forum I am reporting my results using Tom's PAR meter. One of my "discoveries" is that mylar looks like the perfect reflector material, but it isn't. Aluminum foil is much better. Glossy white paint is even better than mylar. This jolting discovery is easily explained: the mylar makes a good mirror in that it accurately reflects what light strikes it, but it doesn't reflect as much of that light as aluminum foil reflects. Aluminum foil is useless as a mirror, because it doesn't accurately reflect what light strikes it, but it does reflect much more of that light than does the mylar. Glossy white paint (and maybe matte white) is a good reflector in that it reflects a very high percentage of the incident light, which is what makes it white, but it diffuses all of that reflected light so the reflection isn't at all accurate. I hope that isn't confusing.

newbie314

Would doubling the layer of mylar help increase the efficiency

hoppycalif

I don't think doubling it would change a thing. It is the metal surface that does all of the reflecting. Light that penetrates that surface is lost, even if reflected with a second layer. The reflected light from that layer would then be reflected again by the back side of the first layer, so very little would make it through to augment the first layer reflection. Aluminum foil is cheap, easy to buy, and works best. Or, just a sprayed on coat of glossy white paint is even easier to apply. I think I will stick with aluminum foil.

newbie314

My hood originally had the white plastic. Wonder if I should go back to that.

Unless the mylar that's shiney on one side and white on the other is better than plan white.

I thought my tank had more light after mylar.
Was real cool with the LED moonlight.

hoppycalif

I'm not sure white plastic is as good a reflector as white paint. I know in bright sunlight a house painted in pure white paint can make your eyes hurt from the reflection. I doubt that white plastic would do that.

newbie314

Yeah your right, never thought of that.

hoppycalif

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.

 

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