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RE: Doubling light output = Increasing wattage??

The reflectors won't double the light output.  I work at an elec. utility
and for energy conservation, we assume that you can replace an open, four
lamp fixture (no reflective surface above the lamps) with a three lamp
fixture equipped with a spectral reflector and have about the same amount of
light on the work surface below the fixture.  And we're assuming
computer-designed reflectors, which the retrofit aquarium reflectors I've
seen are definitely not.  Your hood probably has some kind of reflector
built in if it's a manufactured hood, so you would achieve even less of an
increase by going to an aftermarket reflector.

Plain flat white paint reflects 90-something percent of light, according to
a previous posting on the APD, so you might consider that if your hood
doesn't have a reflector.

Could you fit three T-8 lamps in your hood, then drive them with a high
ballast factor ballast?  For example, GE has a 3-lamp T-8 ballast with a BF
of 1.18.  Assuming that the light output of the 32W T-8 is 98% of the output
of a 40W T-12 (taken from a GE comparison chart), the T-8 will give you the
equivalent of 3 lamps * 40W * .98 * 1.18=138.8 W of light.  Almost 2 W/gal.
The only thing is, since the lamps would probably be very close together,
you'd lose some light because the light reflected from the top of the hood
would be partially blocked by the neighboring lamps.

Here's an excerpt from an email I sent someone else about how I crammed
fluorescent lamps in a small hood.

Good luck,
Wade Shimoda

As for me, our 45 gal. tall (36" wide x 24" deep x 12" front-back) only had
a wimpy single 24" tube in it's hood.  Since it wasn't enough for plants, I
proceeded to retrofit it with stronger lights.  Unfortunately I couldn't use
3' tubes since I wanted to keep the original plastic housing for the lights
(probably not the best choice in retrospect, but it looks totally 'stock'),
which was about a 1/2" too short.  So I crammed two F40/30BX - 741 'biax' (I
think that's what they were.  I'm at work right now.) tubes into the hood
with two sample pieces of lighting reflector material and mounted the
ballast outside.  So now I have approx. the same light output as two 4' T-8
(F32) lamps.  The lamps look very similar to the 'power compacts' you see
advertised.  They run off the same ballast that is used to drive 4' T-8's.
(NOTE: This was back around 1995.  Ballast mfrs. now offer ballasts that are
specifically designed for the F40/30 lamps.  But you can still use some of
the 'regular' T-8 ballasts.)

How did I decide what to use?  Well, at the time I designed it, that size of
tube provided the light level I was looking for within the small confines of
the plastic housing.  And as I said above, they also run off the most common
ballast for T-8's which made availability and price good.

I also chose an instant start ballast instead of a rapid start one because
of the long run times (i.e., long time between on and off cycles).  Energy
consumption is slightly lower and, as long as you have fairly long run
times, say over 4 hrs., the tubes last longer.  For short run times, rapid
start is better because of the less severe 'jolt' it gives to the tube,
which helps prolong lamp life.  The T-8 tubes will usually say 'rapid
start', but it doesn't matter as far as I know.  I don't know if that is
necessarily true for 'old style' T-12 lamps.  Also, when remotely mounting
the ballast, make sure that the wire you use to extend the original wires
are rated for the voltages put out by the ballast, esp. the instant start
ones (they put out higher voltages).

I also added a very small (about 2" dia., 12 v) fan to the housing to cool
the tubes off, since they're over a glass hood and very cramped.  The lights
would probably work without it, but fluorescents are more efficient in terms
of lumens per watt when run at design temp (I think around 78 deg. F).  I'm
guessing they'll last longer at 'design' temp, but can't base this on fact,
and want to keep the tank cool.