I went with glass tops. Some people frown on it due to lack of gas exchange from the water surface or heat build up from lights. Since most light fixtures sold today come with leg standoffs heat build up is in most cases kept under control. For gas exchange from the water surface with glass tops, one solution could be to have a couple of pvc vent pipes at each end of the tank along the back plastic strip. You could even mount a fan on top of one of the vent pipes to draw air out (similar to how an attic or gable fan works on a roof). Also, glass tops collect dust, salts, algae, etc.. which reduce the intensity of the light and therefore require frequent cleaning.
IMO, Canopies may present the same dilemma as glass tops do but they look very nice.
The goal however is to keep the fish in the tank and glass tops are economical.
Lets see what the rest of the group has for suggestions...
