So far we seem to have avoided the heron problem. It probably won't last, but on our side, our garden is smallish and densely planted . The neighbours cat is quite interested, but our pond is edged with new sleepers, so the water level is quite a way down, and just out of his daring reach. My father-in-law has netting over his pond, and complains that he doesn't have frogs. I guess this is why.