WEDDING CENTERPIECES: Instead of floating candles, what can I use to put in a gl vase with water?

My wedding center pieces are going to be something with a clear gl vase with water in it and a mirror for those vases to sit on. My only problem is-- is that the venue of my reception doesn't allow candles. What can I put in those vases with water instead of floating candles? Any ideas? I thought of fake flowers but will fake flowers float or sink? HELP!