Sorry guys havent checked my post in a couple of days and have got so many replies. Thanks everyone.
Tanker - I have got a 6" airstone at the moment, like the amazon link you posted.
Byron, you are making me nervous now :(. The lid came with the tank and fits into place. The electrical part of the lighting unit is ofcourse built into the hood and covered, but it's the tubes which are not covered by anything except for a plastic casing at the terminals. So any water which evaporates or sprinkles because of the air stone will go direct to the tubes :(, although i have kept the bubbles to as low as i can.
The only reason i got the airstone is, since i have a bit of plants, i'm using the spray output mode on my filter Fluval U3, which is apparently suited for plants. So i'm hoping a bit of bubbles from the air stone would cause some surface agitation in turn maintaining the necessary oxygen levels.
In terms of the glass pane, i'm not sure even if i get one, it'll be able to slide in properly between the hood and the tank top edge :(. Anyone else have the fluval roma tanks with this issue?
Byron, on another note, my plant leaves have brown spots all over them?

help please!!!
Thanks