Growing watercress in your pond can provide a great source of this popular food throughout the summer as well as helping to control unsightly algae. Watercress grows quickly and, in doing so, uses lots of nutrients. The more you harvest it for eating, the faster it grows, and the more nutrients it uses.
To get the best algae control, take some shoots of watercress and put them in a glass of water until the roots start to form. Then take the shoots and place them in a planting basket (with mesh sides) and hold them in place with a few stones. Position the basket in the pond margins so that the top of the basket is level or above the water surface; suspend it to the pond side; or pace it in running water returning to the pond from the filter. In a short time the watercress will grow and the roots will come out of the planting basket. The aim is not to provide any planting medium that the watercress can get nutrients from – so it needs to take everything from the pond water.
If you have enough watercress you can remove sufficient nutrients from the pond water to completely control the algae, but you may not have enough space to do so. A couple of baskets provides plenty to eat and makes a difference to algae levels.