I'm building a diy light hood for my aquarium. Under the hood I would like to have a glass/plastic canopy to cover the water surface. I was thinking between using an acrylic sheet or a commercial fluorescent light cover.
Here is a picture of a commercial fluorescent light cover if you don't understand what I'm talking about.

I would prefer to use the commercial fluorescent light cover, but will it affect the intensity of the light? Will it block some of the light from getting into the aquarium? I'm trying to setup up a planted aquarium so I could use all the light I can get. I'm going to have 4 T12 48in bulbs (4X40w) for a 55g.