A friend of mine had a Heron do a number on is koi pond... He has managed to drive it away.
Pat in NH
My father-in-law has a small pond jam packed full of goldfish of all sizes (they breed like wildfire every year) he esimated on 300 individuals on draining it low and re-filling last year. He started with five fully grown back when he aquired the house six years ago.
Grey herons are extremely common in the area, his trick - an adult 'dummy heron' stood on the edge of the pond. Apparently they won't bother going in to steal the fishing spot.
Unfortunetly Herons will stab large fish if given the oppertunity, i've seen a few fatalities and many stab wounds/scars back in my carp fishing days.
Lovely Photos Laura! there really is something great about derelic/old buildings