Preparing a pot for a water garden is not difficult. Because many pots, especially unglazed pots, can leak water even with the hole in the bottom sealed, you will need to apply a sealant to the inside. When selecting a pot for your water garden, consider the size requirements for the type of plant you are planning on growing. Some, like full-sized lotus, will need very large containers to thrive.
Spray the inside of your pot with several coats of clear acrylic sealant. Many pots, even glazed pots, may weep water through the sides and bottom.
Place a rubber or cork stopper in any holes in the bottom of the pot, once the sealant has cured according to the manufacturer's instructions. Trim the stopper if it sticks down too far and affects the balance of the pot.
Caulk around the stopper on the inside of the pot to both hold the stopper in place and fill in any areas where water could leak out.
Turn the pot over and caulk around the bottom of the stopper.
Allow the silicon to cure and fill the pot with water to check for leaks. Once you have verified that the pot doesn't leak, plant your water plants according to the supplier's instructions.