You can't really make a shop light water proof, although you can buy water proof endcaps/ballasts from lfs
to make your own waterproof fixture (expensive way to go tho!)
Do I understand that you are just resting the shoplight on top of the tank? I don't think that is too good. Most people mount it in a canopy of some sort - you simply build a box to fit on top of the tank & mount the lights to it ( this would raise the light off the tank top.)
Failing that, I would suggest hanging the shop light from the ceiling so it is a few inches off the tank.
For protection, I would either have a glass top for the aquarium or use an acrylic sheet fitted into the canopy to seperate the light from the water - make sure you have ventilation slots in the canopy in this case or things might overheat.
I wouldn't bother with egg crate as the top. IMO
, glass top (DIY
or pre-made is the way to go). You can also substitude acrylic for glass if you go the DIY
route - although you would need some sort of bracing for the acrylic to prevent sagging.