depending on whom you ask, most people prefer to keep the glass top off; supposedly will hender necessary gas echange that might even build up causing possible explosive problems so a few have said; also will ADD to your mantainence because you will then have to periodiocally clean it of salt creep itself & possibly algae...do you have a canopy? you can DIY cheap or maybe if not your thing, possibly a friend who is the DIY type could do so for you still quite cheaply; buying quality ready made ones can be about as expensive a new light set...you can also set up your own top off system w/ a float valve to replenish evaporated water for you