madmom
Fishaholic
I have found several nice pieces of river glass on my walks. Most are green but there are the odd brown, clear and other colored pieces. If I sterilize them would they be safe to put in my tank?

I would agree with Kaz that it is safe to use. Assuming you clean them well and boil them. My only concern would be the sharp edges - fish have a tendency to get a little kamikazied out for no reason and could hurt themselves if you aren't careful how you set the tank up. Other than that, I don't see a problem!