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Re: How much light is reflected by a glass cover?

> >All told, I expect a clean cover glass to waste maybe 25% of the useful
> >energy, so it is pretty significant. [Unfortunately, my fish are all
> >killies, and air just doesn't keep them in the tanks. :-)]

There is a special glass known as "starfire" glass that is much clearer 
than the usual soda-lime (greenish) glass. I'm not sure what the exact 
spectral transmission properties are, but it certainly appears to allow 
much more light to pass through. If the glass is a big problem in your 
setup you might check with a glass shop to see if you can get some 1/8" or 
so starfire glass panes to use in your lights.

>I wonder if a wire mesh would be a better option. I've been thinking
>about removing the glass but two things bother me[using powercompact

Use fiberglass mesh -- it will last longer in a high-humidity environment. 
Aluminum WILL corrode over time if it is constantly misted with water, 
especially if that water has any salt or similar compounds in it. Ask 
anyone along a coast how long aluminum lasts in the salt spray and you'll 
see why this is a concern

Steel mesh is usually hot dip galvanized, and you don't want the zinc run 
off getting into your tank. Zinc strips are often installed at the peak of 
roofs so that the runoff prevents algae and moss growth on the shingles to 
take advantage of this -- zinc is toxic!

If you need the mesh to handle high heat then Al is probably your only 
option, but I'd try to use fiberglass if at all possible.

>1) Water splashing on hot tubes could cause failure.

Not usually a problem if your lights are suspended high enough above your 
tank, but this will depend on your particular setup.

>2) Strip light accidentally getting knocked into the tank.

Any fixture dropped into the tank will be a problem, with or without a 
cover glass. I have had success building "springy brackets" to allow me to 
snap little 13w PCF fixtures into the rim around AGA tanks, but I've never 
tried it with anything larger than the AH Supply 13w PCF fixtures. For any 
open-top tank I recommend secure light mountings AND a GFCI to help prevent 
a dropped fixture from becoming a big problem.

BTW, those "springy bracket" fixtures use no cover glass, and hold the bulb 
about maybe 5-6" above the water surface. Even with a bit of mist coming 
from the air-driven filters in those tanks, I haven't had any bulb breakage 
and the reflectors only need occasional cleaning to wipe off the mineral 
deposits. I've been running the lights for about 3 years now this way.


Waveform Technology
UNIX Systems Administrator