Mesh Screen/Cover for Tank?

I've got a 55 Long Reef Tank open top with the Coralife AquaLight Pro MH w/Blue Actinics. The light structure is mounted on legs about 6" from the top surface of the water. Would it be risky from a heat standpoint to get a mesh screen cover for the top? I'd like to weigh the options as I have already had 1 fish jump out (firefish) and would like to avoid losing as I continue to stock my tank with more fish. As of now I only have 2 Clowns and a midas blenny.



Thanks for any suggestions anyone might have for me, much appreciated!