I didn't even think about them not floating - that's one of the qualities I look for in a potting medium. Can't wait to see how your two plants take to this method.
I think there's a chance it won't work as well as I thought. It seems to be drying out very very fast. I'm not sure if it has good capillary action either.. Was reading and saw that that is a good attribute. I threw some in a cup with water at the bottom and will see if it can make its way to the top.