You can also place a pot direct into your pond; make sure the water is the same levels as your pot to start with, then gradually increase the water level as the foliage grows.
For small varieties keep the water 50 – 150 mm higher than top of the soil; For larger varieties water need to be 1 m deep from the top of the soil.
How to grow lotus in a pot
Choose a pot at least 300 mm wide and deep and position in a full sun spot.
Fill the pot with heavy garden soil (or 2 parts of clay + 1 part of river sand) for at least 150 cm deep, plant the seedling into the soil 20 - 30 mm deep, cover the mud with some pebbles, add water carefully and make sure water level is 5 cm higher than soil, but do not submerge the leaves.