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Re: Metal Halide

Karen Randall wrote:

> Actually MH and fluorescents are nip and tuck when it comes to lumens per
> watt.  Normal fluorescents are slightly lower, energy efficient T-8's are
> slightly higher.  All are _far_ superior to incandescent.

> And, yes, the 2w/g guideline does pertain to MH's too.

Since MH is a more of a spot light, one should be able to get
away with less than 2w/g by keeping the light hungry plant
directly under the MH and the less light hungry plant away
from it.

I also believe (not 100% sure) that higer wattage MH is more
efficient than lower wattage ones.  So one can also use less
than 2w/g if 400W MH is used instead of 175W MH.

Since we are on the topic of metal halide, electronic ballast
for 175W MH is now available.  Aquarium Frontiers recently has a
test on this ballast. The article claims a 175W MH lighted
with electronic  ballast is as bright as a 250W MH on a tar ballast.
The test is done on 10000K and 6500K bulbs.

It is still too early to make a conclusion.  No one has reproduce
the test result and no one really knows the reliability of
electronic ballast and the effect on bulb life.  The test is also
not done on 4100K and 5500K bulbs, which are more applicable to
planted aquarium.  However, I have to say electronic ballast looks
very promising.

See http://www.aquariumfrontiers.com/1998/april/product/default.asp
for detail.

Louis Lin