Sorry to hear Laurie...total bummer when you find them on the floor.
Check out my thread and the cover I made...I really don't think there is any lost light with the mesh (nothing like eggcrate) if you really do want a cover.
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45 Gallon Cube with 10 Gallon Sump, Lighting 8 bulb T5, Vertex IN 80 Skimmer
-2 Occelaris Clowns, Engineer Goby, RBTA, Peppermint Shrimp