Netting is the best option but if that is not feasible then stringing fishing lines across the pond is worth a try. If you are going to use drain pipes for shelter, don't bother to cut them in half. They can get overturned. Make sure that the pipe is long enough and wide enough to house your largest fish and they will want to crowd into the same pipe so make allowance for that as well.
i posted this on the other thread but what about as well as the netting getting a deer scarer it just a pivoted piece of wood thats hollow and fills up at one end and when it get too full it bangs down making a loud noise if deers hate it then i bet a heron will too and you can put it next to the pond so the water can go round and round