Why net over your pond? Well there are several good reasons that spring to mind.
From the maintenance point of view it saves all those pesky leaves from blowing into the pond, not only are they unsightly but they can get sucked into your filter units clogging everything up or sinking to the pond floor creating a slushy mulm.
Netting can keep cats, dogs and other wild life out of the pond too – it may even deter Herons as they don't tend to like it much either, although Herons can be very persistent!
Pond fish are also notorious for being 'jumpy' especially in the warmer summer months... we hear countless tails of disaster because a fish has been found out of the pond on the lawn etc after jumping for those delicious flies...