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Re: light intensity
George wrote:
As I've been reading the APD for lo these many years, one thing has been
bugging
me - the amount of light people use. FAQs and Urban Myths generally
recommend
"2-3 watts per gallon", a relatively crude measure that attempts to
compensate
for potentially poor quality FL bulbs (like shop lights with crummy lumens
per
watt and spectrum) and potentially marginal hoods with poor or no reflectors
(such as come with aquariums).
I've been hugely successful with 1.6 watts per gallon of FL light using
Triton
and Penn Plax Ultra Tri-Lux bulbs in fixtures with typical reflectors placed
about 4" above the water. And thesea re 48" bulbs in a 60" tank! Since the
MH
bulbs in the 120 are suspended above the water, the amount of light at the
water
surface is the same as in the FL tanks (15,000 lux) and is not really like
"2.9
watts/gal".
1) What level of lighting do the experts use (Tom, Roger, Neil, Karen, Erik,
Diana, Charley, Jon, ... you know who you are)?
I reply:
I am no expert so I guess I shouldn't reply but here goes anyway.
I think the watts per gallon rule is so inaccurate that it can never be more
than a rough guide. You can never be sure that the watts/gallon really
indicates the one tank actually has more light than another. We need a
photon per gallon rule which as it turns out is very difficult to calculate.
You have to take into account things like lamp efficiency and fixture
efficiency and you can't just go by the nominal wattage on the lamp, you
have to know the true wattage that the lamps are consuming. Most of that
information is not readily available. For instance, I use 1.6 watts per
gallon over my 120 gallon tank and I can grow lawn type plants. This is very
misleading though, as I use 1.2 ballast factor electronic ballasts with RE
phosphor 32 watt T8 lamps and pretty decent mylar reflectors. The electronic
ballasts improve the efficiency of the lamps and the high ballast factor
overdrives the lamps. RE phosphor lamps are also supposed to be 7% more
efficient than other lamps.
George's system may produce quite a bit more light than the lamp wattage
actually indicates. I would very much like to know the current and voltage
across the lamps in his system so I could learn the wattage his lamps are
actually consuming. One of the most interesting things about George's setup
is that it is not fully optimized. I don't believe he uses electronic
ballasts and if he did there is a posibility that he coud obtain ballasts
with even higher ballast factors than he currently uses. Maybe he could
obtain the same results with only 3 lamps. ;-)
Wayne