- 1). Dig a trough around the perimeter of your pond, about two inches deep.
- 2). Plant flowers or other plants within the trough. The trough will capture rainwater, which washes algae-promoting nutrients into your pond, and the plants in the trough will absorb any remaining nutrients.
- 3). Scatter water lilies over about two thirds of the pond's surface. These will not only absorb excess nutrients but block sunlight, which also promotes algal growth, from reaching the water.
Source...