I'm not sure painting it was a good idea as black absorbs light and white relects it, they make a silvered type also if you can find it. Also I've been looking into adding eggcrate to the bottom of my fixture cause I read somewhere that dana riddle recommended it, so I did some searching and this seems to be the consensus:
1) make sure the thin side is up - it will focus then not disperse light
2) make sure the light source is within 3 inches of the eggcrate
3) but according to anthony calfo flourescent lights more then 3" from the water surface are just about useless, so that works well anyway
conclusions - I'm thinking about two experiments right now. On my 20 I placed eggcrate right on the tank and set my fixture (flourescent) right on top of it after removing the legs, hoping that this increases the overall quantity of light entering the tank. Also I am planning on adding some to the bottom of my MH pendent fixture to see if more light ends up in the tank then on the walls and floor
I know this is outside the realm of your question but since I did some reading I thought I'd share what I learned.
