not just at night they hunt in the day too.Do them fake herons work round the pond?Only if you keep shifting it about, them heron reflection balls are better http://www.amazon.co.uk/gp/aw/d/B00BAUOJSS/ref=mp_s_a_1_15?qid=1458525448&sr=8-15&pi=AC_SX236_SY340_QL65&keywords=heron+deterrent
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Cheers, D.
It's what we use now, apart from my staffy likes chasing the things from my pond