For my tank I had glass tops but stopped using them as it gave very little distance between the T5 fixture and the glass top. This seemed to cause the fixture to get a bit too hot. I found the tops would also require cleaning every couple of days or the light would become blocked by salt buildup and algae.
I stopped using this and had a Percula clown jump out of the back of the tank.
I still have an open top but now have a barrier around the tank to hopefully stop anymore jumping. To make it I used some extra baseboard that we had from our home renovations and build it around the front of the tank.
For the back of the tank, since I had so much equipment and wires with the skimmer, phosban and carbon reactors I made the wall out of Lego Blocks
It doesnt look too pretty but it allowed me to build in holes for all the wires and piping.