Pam, the way to insure that no water will escape through the hole or 'sweat' into the pot, is to use a plastic liner. If you can't find anything that fits the pot you might look for something tubular shaped (empty tylenol containers, prescription bottles?). You could put the water and the bamboo in the container and then put the rocks in, around and on top of it. Good luck.

Pam, You can use low temperature glue to fill the hole and then make a slurry of silacone caulk and mineral spirits. The slurry should be just thin enough to apply with a paint brush. Paint the inside of the pots and the silacone will fill in any cracks. For outdoor pots, use RTV glue to fill in the hole or glue a cork in place. It will adhere even when faced with expansion and contraction due to heating and cooling.