George Patterson wrote:
Wayne Sallee wrote:

So many people purchase lights without figuring out the watts per gallon.


I've been thinking about this, and it doesn't seem right. Different
types of lighting have different efficiency characteristics. The usual
standard for measurement of light is lumens. Spectrum is, of course,
also important in this field, but I think that lumens would be the most
important figure for measuring intensity. Watts per gallon would only
work when comparing two fixtures of the same type; for example, two
fluorescent fixtures.

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.
George,

You are correct. Watts per gallon are just about meaningless, since it
does not cover the depth of the tank, nor the light source. But with no
other info it can give you some information.

With lights another important thing is the reflector. This is why a 4
bulb 54 watt T5 setup will put out as much or more light than a 4 bulb
110 watt VHO light setup. The single bulb reflectors for t5 bulbs are
much better than what is normally used on t12 vho bulbs. It is also why
a 250 watt HQI metal halide can produce more usuable light than a 400
watt single ended bulb.


On Lumens. To use they don't mean much since red light as many lumens
ase blue light and the red does not contribute to photosynthisis. For a
good measurment you need to find out the PAR of the lights. Which is
very hard to find. You will find that there are some hobbiest that are
publishing PAR data for some light, but most of them are on Metal Halide
light.

To be honest any time I see somebody use the watts per gallon measure
ment I cringe. 250 watts over a 65 gallon hex tank is a lot less
usuable light than 250 watts over a normal 65 gallon 4 foot tank since
everything is closer to the lights on the 4 foot 65 gallon tank than the
65 gallon hex.

Kim Gross
www.jensalt.com