Hi magick81,
There's no reason why you can't use a glass aquarium as an enclosure. I have Pygmy Beardies, Central Netted Dragons and Central Beardies in wooden enclosures, glass terrariums as well as a 2ft glass aquarium.
What you need to remember about glass tanks though, is that it loses heat faster than say a fully enclosed wooden or melamine enclosure. What type of beardies are you planning on getting? 3ft is a good size tank but if you're getting vitticeps for example, especially if you plan on housing more than one, then a 4ft or bigger is probably better.
I have an adult male Pygmy Bearded Dragon in a 2ft open top glass aquarium. I have about 2cm deep of sand substrate along with the usual ornamentation such as rocks, silk plants and a forked resin branch. He's perfectly happy in it and I don't have any issues with loosing too much heat.
The tank is too tall for him to jump out of so no worries about escaping. I have a small diameter ceramic lamp holder (clipped to the side of the tank) with a 75W daylight bulb which is on a timer, set to come on about 7am and switches off at 6pm during summer. (In winter, this is shortened by 2-3 hours, emulating natural seasonal cycles.)
I also have a Reptile One 2ft aluminium T8 reflector which I use with a 10.0 UVB tube. The reflector sits right across the top of the aquairum and covers half the aquarium already so I kind of get a half lid at the same time which helps to trap the heat in for a bit longer. Between the heat coming off the reflector and the 75W daylight bulb, my temps on the tank floor at the basking spot gets up to mid thirties+ on a normal day.
Down my cool end, I have a big silk plant with lots of leaves, which I drap over the resin forked branch and this provides a cooler, shady area for my beardie to sit under when he gets warm enough. You do have to be very careful on those really hot days though. I usualy switch off the 75W daylight bulb if I know it's going to be a stinker of a hot day.
I would also recommend sticking a piece of those aquarium background landscape picture things - you know the ones where you cut whatever you need off a big roll at aquarium shops? I've managed to find some that look like a rocky, desert type landscape and I have the film stuck on the outside of the aquarium on the back and two sides. I find this makes my beardie scratch the glass a lot less. I think because it's glass and he can see out, he wants to try and get out. So by sticking the landscape pics on the three sides, it almost stops him from scratching the glass and he seems very content and happy in his tank now.
Lastly, I have a dual probe LCD thermometer which I put one probe on the cool side and the other probe on the hot end so I can monitor the temperature gradient. I don't use a thermostat although I probably should, but this particular tank is in my study room and it's relatively cool in there with good ventilation as I leave the window open a bit all the time so I am not too worried about it getting too hot. With some careful experimentation and close monitoring of temperatures, I know exactly how hot my tanks get so I am quite comfortable not having a thermostat but I am certainly not recommending that to anyone else. It's always safer to use a thermostat.
If I can figure out how to upload photos to this thread, I will try and post a picture of the above enclosure. Hope this helps. Best of luck.
