Pond nets should be spread across your pond in the fall to keep dead leaves and twigs from falling into your pond. If debris builds up at the bottom of your pond the water will be prevented from getting the oxygen it needs to keep your fish healthy and filtration system operating. Pond nets are also an effective way to keep predators away from your fish and pond vegetation. Repeatedly skimming your pond with a hand-held net on a pole will keep leaves from quickly build-up. Pond netting is made of solid plastic or nylon, and typically comes in 3/8-inch mesh. Pond nets range from $14 for a 7-foot x 10-foot net to $112 for a 17-foot x 100-foot net. Heavy duty, solid plastic mesh nets cost between $90 and $160 online.