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[APD] Re: WPG rule
Yeah, yeah. The watts-per-gallon rule is terrible. Actually, I don't think
there is a rule. Wpg is just a measure that has found some usefulness. If
you don't like it, then come up with a new one.
It's important to know what kind of lights and what kind of reflector you're
talking about when you use a wpg measure. 2 wpg using NO fluorescents in a
home-made cabinet without reflectors is not the same 2 wpg that you get from
large PC lights in good reflectors. If you need to judge how much light
someone has on their tank without seeing the tank then you need to know the
kind of lighting as well as the number of watts involved.
This came home to me pretty solidly last week. About a week before
Thanksgiving I finally got tired of my 55 gallon setup that used 4 old
Philips C50s and magnetic ballasts. I went out and bought 4 new 32 watt high
efficiency Philips ADV850 T8s and an electronic ballast and replaced the old
setup. It still doesn't have much of a reflector.
The setup went from about 3 watts per nominal gallon to 2.3 watts per nominal
gallon and the light got *way* brighter -- probably about as bright is I
could have gotten if I added two extra C50s to the old setup to get 4.4 watts
per nominal gallon. By Thanksgiving the water was turning green. It
eventually went to pea soup before I got it back under control.
There are a lot of factors that make wpg a sloppy measure. If you have a
better one then let us know about it.
As far as how many wpg you need, I think that's mostly a matter of personal
choice. People who are just starting out and people who don't have a whole
lot of time to spend taking care of their tank should stick to 2 wpg plus or
minus with allowances for smaller and larger tanks. Higher light levels
don't let you grow all that many more plants but higher light levels do make
photographs look better.
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