Effects of FL bulbs close to eachother?

	I recently acquired a 55 gal Seaclear, which comes w/ a black!
acryllic hood and is set up for one 3' bulb.  So I installed 3 3500K, 25w
bulbs run by an electronic ballast, and a Triton and an Ultra Tri-Lux run
by one of those non-electronic ballasts ... I also spraypainted the inside
of the hood with white Krylon.  Two questions:

	The bulbs are about 1/2 inch apart.  Will this cause problems,
light loss, etc.?  I noticed in another post the statement that there
would be some light loss frome bulbs in close proximity.  Could someone
explain, refute, elaborate?  Also if this is a problem, could I solve it
by placing say, tin between the bulbs? If nothing else, I reckon doing so
would help focus the light downwards, right?

	Another curious thing happened with the two-bulb part of the
set-up:  The ballast (an Advance) is UL listed for two 40w  bulbs, and CSA
approved (good enough for us Canucks ;-) ) for two F30T bulbs.  At the
time I bought the ballast, I thought that meant I could run ANY 30w bulb.
Curiously, it will not run two 3' Aquarilux.  At first I thought my wiring
was wrong, when thye wouldn't light, or lit dimly.  But I tried two 4' 40w
bulbs and no problem!  Then I tried two 3' 30w Ultra Tri-Lux, and again
nor problem.  Finally, I got smart, and noticed that the Aquarilux are FL
30, not F30T.  But why the HECK would that make a difference?  

	The light combination, btw, looks just fine, and the 3500K bulbs
were nice and cheap, unlike (ahem) the Triton and Ultra Tri-Lux I added to 
improve the colour rendition.