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Re: heat from lighting -- getting light from heat

Diane Brown asked:

> I have three 29G tanks running with the original Eclipse3 light
> fixtures (2
> T-8 20W bulbs) and a separate GE stick-on 33W gro light--net 73 watts
> standard fluorescent lights, no reflectors worth the name; with
> heaters
> unplugged, and those lights on for 10 hrs/day my tanks are 82-84
> degrees in
> a 74-76 degree room (summer temps) (The Eclipse hoods have no
> significant
> vents.)  Those temps are ok for the loaches and chromides, but too
> high for
> the goldfish (and maybe for the cabomba that used to thrive in that
> tank...).
> If I switch to the AH supply 55W compact fluorescent fixtures with
> their
> reflectors, am I likely to get equivalent or better lighting with
> less heat
> to the tank?
> Would deep-sixing the Eclipse3 all-in-one system and going to a glass
> hood
> with AH lights above the glass give me any further temperature
> benefit?
> I'm trying to avoid the noise and additional energy use from
> fans....but
> don't want to cook my goldfish.  One of them has been pretty punky
> since
> the heat really hit....
> Has anyone made this switch and noticed a temperature change?
> Thanks for any and all input to help us all "chill out".

In general, electric lights are really heaters that give off light;  in
other words, they do a much better job of the former than the latter. 
Really good electric lights that have more than just a smidgen of the
spectrum are about 35% efficient if all the light is usable, which is
rarely the case even with really good reflectors.  [Some lights of only
one narrow color can be as 65% efficient or higher -- think godawful

Assuming you want the light *and* ambient room temps adjustments are
out of the question ("Hey, who turned the thermostat down to 65?"),
then the only ways to keep the heat out of your tanks is to insulate or
ventilate, or both.  A glass cover (insulate) can help or hurt.  It
will insulate in both directions.  If it reduces heat loss from
evaporation, and that reduction is greater than the insulation gain, it
can hurt.  Hard to guess what will happen in your particular setup.

Raising the lights up away from the water (insulation & ventilation)
*and* providing for good air flow (ventilated hood) are your best bets
for noiseless cooling.  The more ventilation openings you can stand
(some light always leaks out, too) the better for losing heat into the

Whatever fluorescent lights you use to put the same number of watts
under your existing hoods will produce pretty much the same heat
effect.  45 watts of heat (70 x 0.65) is 45 watts of heats however you
get it there.

An AHSupply reflector might let you use less watts for the same
into-the-tank-light, and therefore reduce your heating somewhat but I
really doubt that it will buy you as much help as you're looking for. 
I recommend them anyway but that's for other reasons.  

An AHS 55PC, with the ballast remote, might give you an *acceptable*
(but not the same) level of light and an appreciably lower tank temp. 
I'd consider trying that.  I don't recall the depth on your hoods but I
think an AHS 55 will fit.

My friend across the street keeps gold and koi fish in his shallow pond
year round.  They seem to thrive and temps go from near freezing to
well over 80 degrees F.   So maybe your fish aren't happy but maybe
they are so bad off as they pretend ;-)

Scott H.

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