I built this cover with "bird netting" and I really do not see any reduction in light getting through. It's not 100% jump proof but it stops most. The smaller ones could still squeeze through if they aimed just right! It's 1" squares I think.
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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