Before the tree leaves begin to fall, install a good quality pond net and tent over the entire pond surface of the pond, stream, and waterfall area. This will keep falling leaves out of the pond reducing your work in pulling out excess decaying leaves and prevent organic buildup of debris on the bottom of the pond. The more you can keep out in the fall, the easier your spring opening will be for you. Make sure the net hangs over the pond by at least 6 inches. This allows you to roll up the net at the edge and secure it with ground staples/pins. Be carefully not to stake the pins through the pond liner.
We like to keep up our netting off the surface of the pond using a pond tent. This helps the leaves to blow off the netting rather that weigh it down into the water where the leaves can tint the water brown.
We keep our netting on through the winter to protect the fish from predators like the blue heron.