Damn kookaburras and Herons! We have lost so many of our pond fish to birds over the years and sometimes all you can do is put some netting over the pond!
At least until the birds have forgotten about it.
The pond netting we sell stretches out to over 4.5 metres in wide, so you just need to select how many linear metres you would like to purchase. You can affix the netting to a frame or just drape it over your fish pond using rocks to anchor it above the water surface.