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Re: Your suggestions for lighting please [f/u]

Thanks to all who offered their thoughts on my rather broad set of questions
regarding lighting.
It seems that the consensus is that a target of approximately 225 watts for
my 48 x 18 x 20 tank is about right.

Compact flourescents seem to be the most popular choice. Some of you like
metal halides and some don't. MH advocates agree, however, that one bulb is
inadequate for a four foot tank, citing a 2 x 2 per bulb rule of thumb. I
thought that presented a quandry (2 x 175 = too much light?) until someone
pointed out that 100 watt MH bulbs are available. Several people indicated
that they still use NO flourescents with good success. And VHOs may be
falling into disfavor?

Sounds like dimmability isn't much of a factor for most people. Some choose
to stagger the on/off period of different sets of light to approximate the
dawn/dusk periods. I like that idea.

A couple of follow-on questions:

- what do you suppose is the optimum color temperature for my lighting? I
understand that 5500k bulbs most closely match sunlight (at the surface
anyway). Is it safe to assume that most tropical FW plants are shallow water
species and that bulbs designed to meet the needs of reef aquarists, i.e.
actinics, aren't applicable? Some suggested 6500k bulbs or a mix of 6500k
and 5500k. What's the rationale there?

- somebody mentioned noise as an issue related to MH. Would that be the bulb
or the ballast? Is that a wide-spread complaint?

- commercial lighting products seem to be available as "retrofit" kits
where, presumably, the hardware is attached by me to the inside of my
canopy, or as complete ABS or wood hoods. It looks like these hoods are
intended to be placed directly on the top of the aquarium and have lenses of
clear plastic or acrylic. Are these meant to fit inside or underneath the
existing canopy or would I have to do away with it? (I wouldn't want to do
that - the canopy looks nice/matches the stand and it was very expensive).

- with a DIY or retrofit kit I guess I'd be mounting the reflector directly
to the underside of the top of the canopy, correct? This would place the
bulbs several inches higher than if they were in a hood placed directly on
the aquarium. An eyeball measurement says about 8 inches, actually. Will
this appreciably impact the amount of light reaching the bottom of the tank
and thereby require more wattage? If so, how much would you say?

- lastly, in the DIY or retrofit scenario, should I leave openings in the
acrylic top uncovered? Are there issues with humidity or moisture affecting
the bulbs or connections? Is there actually a risk of water splashed from
the surface shattering an MH or CF bulb?

Thanks again,

Tim