I am by no means an expert but my take on it is yes egg crate blocks some light but it is minimal and you have to wiegh this with the danger of flying fish. As for evaporative loss my understanding is as long as you top off consistantly it can actually work for you by helping with cooling your tank .
Most of the tanks I have seen are topless and this must be for a reason.
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Biocube 29 est 05/05/08, Koralia 1, 30lbs live rock, ,yellow tail blue damsel, pair cinnamon clowns, baby snowflake eel,Toadstool , metallic green mushroom, assorted zoos , kenya treen
180gall display, 190 pds live rock, virgate rabbitfish,bluejaw trigger, bubblletip anemone,yellow tang, sailfin tang,melanarus wrasse, cloud wrasse,
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