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Re: light on aquariums

John wrote:

It's simple....decide which type of bulb you like and
shoot for 2-4 watts per gallon. If your tank is
deeper, then shoot for more light. Also, surface area
is a consideration. A 40 gallon breeder will require
better coverage than a 40 gallon standard. Metal
halide or NO flourescent it doesn't matter. No one
uses incans anymore.  MH are just a better way of
getting more light onto a smaller area...this was
before PC's.

The most important thing is coverage. Get light into
all of the nooks and crannies.

This topic has been beaten to death. The watt/gallon
rule is kinda silly. I know it's not going anywhere,
but it's not valid. Watt/surface area is a better
rule.  That's why *lower* light per gallon works on
bigger tanks.


2-4 watts per gallon will very likely give you anywhere from low to very
high lighting but no guarentee. It is not a rule, but an observation
that this is what many experienced plant growers use. It is not very
useful for predicting what plants you are going to be able to grow with
a given light fixture.

As far as watts per surface area is concerned, what you are saying is
that a a tank with a 4 square foot footprint requires the same amount of
light if it is 6" deep or if it is 20" deep. The fact is a 6" deep tank
that can grow Glosso with not be able to grow Glosso in a 20" deep tank.
Despite the light tube effect, depth matters. It is obvious to anyone
who cares to look at a planted tank and observe the growth near the
water surface and near the substrate or to anyone who cares to measure
the light levels near the water surface and near the bottom of a deep