I run open top tank on my reef. I bought some eggcrate but never bothered to use it. I got my hands in the tank to much. lol But, I could see how it would decrease the light. The light can only shoot down through the egg crate. So, the only real light you get is right down the middle, the rest would be blocked somewhat by the thickness of the eggcrate. I know what I mean but not sure I'm saying it right. lol
Open top is ok Meredith. IMO
It's what you prefer. Just gotta be careful what you put in the tank as far as fish that are known jumpers. And, keep the water level up so there is no splashing onto the bulbs.