Planted Tank Obsessed
Join Date: Apr 2011
Location: CA, United States
Water deposited on the cover by condensation will not affect the amount of light penetrating the cover, but it might disperse it more. It is usually not an issue at all. There's no need to remove the condensation.
Water deposited on the cover by splashing action of the spray bar works the same way as long as it remains liquid. There's no need to remove it either. However, this water will leave mineral residue as it evaporates. This residue will block light, so you will have to clean the residue from the cover from time to time (like, once a week).
And, BTW, Lexan (polycarbonate) is not Plexiglass (acrylic).