Thanks for all the comments.
the light is 30" to the bottom of the tank, so that's 21" to the surface, it's a 250W MH so it should be sufficient to this little tank.
for the bottom, I am going to cover it with 2 nicely painted panels same as the color of the wall, so all you will see is the tank hanging in the middle. that's one of the next thing on the to-do list, along with painting the huge black cable white and putting a skimmer in.