The key to a healthy pond is keeping the water clear and ensuring that plants do not take over ... bedded down and that the soil is compacted around the sides to support the water pressure.

Trim the sides of the liner leaving a 30cm (12in) overlap around the sides of the pond. Cover these with paving ... causing it to perish. Position plants and add oxygenators.

"We only found a handful of these plants in the pond but we're hoping to cultivate ... the plant is found in a few isolated populations growing around lakes and on muddy open ground.