Lid Query

I was wondering what exactly constitutes a proper lid for an aquarium.
My 5 gallon didn't come with a lid, so I measured and made a flexible plastic cover from a Bath&Body Works Robe box (a clear plastic gift box). I cut a space in the back for the box-filter to fit and also a space for the heater cable. This prevents much evaporation but also provides space for oxygen to flow in/out.
My small 2.5 gallon (that is not set up), however, comes with a glass lid that covers the entire top of the tank.

Should the lid leave an open space for oxygen flow? Or if there is a hood/lid that covers the tank completely, would you get enough air exchange from just opening it everyday to feed the fish?

Many of my rearing tanks have a piece of plexiglass 1/8"-3/16" thick. I made them from scrap pieces. Really low-dough. But, they work and that's all that matters.

That's neat - thanks for the reply. Does the plexiglass cover the whole top of the aquarium? Is there a hole for the filter or heater cables/air tubes?

Maybe you could drill some small holes in the top of the tank. I don't know if the glass would crack, but I am sure that some holes can supply enough oxygen, as well as opening and closing the tank when you need to.

I clipped the corners to allow for air lines. That's about it.