Am I better off without glass covers?

There are a number of facets to this that I think youll have to weigh in on to find out what's most important.

It may be a necessity if you have jumpers inhabiting your tank.

A glass top helps mitigate evaporation but it will also have an impact on gas exchange at the surface of your water. CO2 degassing shouldn't be significant without a cover so long as your return lines aren't causing the water to break at the surface. Tom and many others on this board keep an open top on their tanks. Getting as much as you can in terms of gas exchange is very important if you're using canisters and have no surface skimming....Might be worthwhile investing in a $10 skimmer to connect to one of your canisters if you don't have one already.

The iron content in the glass will inevitably reduce the light entering the tank somewhat, you can see this in a comparison of regular glass vs. low-iron Starphire on the front panel; the starphire shows greater colours (i.e. it lets more light through to your eyes) but I don't necessarily think it will have a tremendous effect. You could always try a PAR meter with and without the glass if you have access to somewhere you can rent one (maybe your LFS?)

Overall I'd say you can run the tank open topped if your fauna permits, tweaking your pump return lines to ensure you have current but no breaking water. It also makes maintenance easier by a bit.

 

There might be one more consideration is, retaining heat. If your aquarium is in a cool basement or cooler part of the house, your aquarium heater might run more than it would if it had a cover. My aquarium doesn't have a top frame so I can't easily provide a cover. If I did, I would probably use one because the 300 watt aquarium heater comes on even in the summer. If light were an issue, I could burn the third bulb. I lose over 2 inches of water between weekly water changes as well. I don't miss the cover getting in the way during cleaning though.

 

Good point. One other thing I should mention is that with high evaporation the glass cover will have a tendency to get covered with algae and scale. Always hated that about the glass cover on a previous tank.

 

Ahh that's right. I forgot about having to clean off algae and calcium. Maybe, I can live with a little higher electric bill after all.