FWIW I have one tank with an open top and another with egg crate. If I wasn't worried about my flasher wrasse carpet surfing, my 75 would not have the egg crate. Another option if you have fish who like to jump is to make a screen top from a screen window kit (about $10 at a hardware store) and 1/4" screening which is available from Bulk Reef Supply for this purpose. The downside to the egg crate is it's very noticable and (IMO
) unattractive. It may create a grid shadow in your tank as well. (It's not really noticable in my 75, at least to me) The up side is you can trim it to still fit pretty snuggly around any overflows, cords, or plumbing you might have. In any case, I lost two other flasher wrasses from my 37 and perhaps a royal gramma as well. When I set up my 75, I knew I wanted to have a flasher wrasse and learned the hard way from my mistake.