Agreed with Gwen. Unless you have a compelling need to keep the lids on (such as evaporation and you have no hood), all they will do is get covered in saltwater condensation and lower the amount of light passed which will require regular cleaning.
Egg crate allows evaporation while keeping your fish from jumping. You can find it in the drop ceiling tile area of Home Depot or Lowes. It's the white mesh lighting diffuser that they sell for drop ceiling lights.
You can get the egg crate at lowes or home depot in the flourescent lighting section. It also lets heat escape easier from your tank. Brought mine down 2 degrees.
Keep in mind that egg crate also lowers light into the tank by up to 80% and more if you install it upside down. Eggcrate is called a difusser for a reason.
I personally covered the back of my tank with eggcrate (about 5-6" from the back) and left the front open but I have a canopy with an open back so I was just trying to stop fish from jumping out the back or into the overflows. It is possible for a fish to still jump out, but it won't be easy.
