if your concered about the egg crate, add netting to it, the egg crate works but I did have a blenny get out anyway, once your egg crate is cut to fit just attach pond netting to it. Ass far as egg crate and lights, technically its a light diffuser so yes will will have a small effect, MINIMAL for this application however do not paint it black,( voice of expirience) it will have a noticable drop in light.