Due to the high heat caused by lighting its pretty common for people to not have glass lids on their salt water tanks. Some fish like to jump though...
What I have seen recommended and plan on doing to mine is to go to home depot and get those sheets made for industrial type florescent lights. They have a few types, but one is a white plastic open grid which will allow light in, ventalation, and some protection to the fish. Its also easy to cut it where needed for filters and other hoses, etc.
-Scott