Here are my thoughts
Personally I think both ideas of adding another light, and lowering the existing lights, have merit. If reality wouldn't keep getting in the way, I'd have more lights in my canopies too (but since I already have 5 halides on the go as it is ..... did someone say "power bill" ?? Trust me, my power bill is bigger than yours any month!!! :P )
I personally feel that a mixture of bulbs yields the fuller spectrum than any one bulb type could provide. Where one bulb may be weak, another may be able to "pull up the slack" so to speak. The only thing is if bulbs have a vastly different colour to them you may get uneven colouring in your tank. When I first went into halides I had one side 14000K and the other 10000K so I could see what I liked better. The unbalanced look, while I was decided, was striking. It's very unnatural looking.
10000K is theoretically not all that a huge contrast (not as bad as say 14000K or 20000K). So a supplemental 175W/10000K sounds like a good idea.
Since we're talking about supplemental light, you may wish to consider the light without a reflector (or maybe just a flat reflector above the light), so to spread out the light. As Ross points out the further away from the light, the less light going into the water at that point, but I don't think that's a concern in this case because 1) this is just to supplement a little bit, and 2) it will help to "blend" the light zones somewhat. At any rate it is something you can try first, you can see what you think, and then decide whether to spend the additional $75 on a parabolic reflector.
Also, about lowering the lights .... again as Ross pointed out (but it was sooo boring to read :P ), the intensity falloff is exponentially proportional to the distance of the light source (note to you grammar nit-picks ... I said the "falloff" is exponentially proportional, which should be the same as saying "intensity is proportional to the
inverse of the exponential distance" ... ow my head hurts never mind). If I could get away with it, I'd have my lights 1" above my water surface!! If I pay $10-20 per bulb per month, I feel better knowing that as much of that light is "useable" rather than being discarded by bouncing off this or that, cover glasses, attenuation, etc. etc.
Anyways just my $0.02
PS. Adding another light is going to stave off your boredom for about .... well, 2-3 hours, tops. So don't put a lot of stock in this to help you deal with your fidgetiness ....
:P
