As you can see from the photos, raised pots give the illusion of a bed of sand at the bottom. Water-loving plants thrive in these sunken pots full of garden loam with 25mm of pebbles on top to stop the fish digging for worms.
Apparently the "water has never been cleaner!"
Although water plants can be expensive, some councils offer plants and fish as an incentive for these types of conversions. Ask your local council if you are interested.
Of course if you are interested, Assured Handyman can help you make it all happen!