Fish being Koi

We've had to replace our lovely gold fish as we think (almost 100% sure) a heron has had them for his/her breakfast.  We have now netted the pond and are thinking about sensor security lighting, installing sentry posts and 24 hour security guards or we might just keep the simple netting.  I took this picture with my iPhone of some gorgeous massive Koi's but they are too big for our pond, i just loved their eyes, they looked so intelligently at me!