One of the things I have learned during my pond management duties (or more accurately put - pond mis-management activities) is that you can never be completely sure what is and is not in a pond. Well perhaps never is a strong word but you get the point.

Fish have a way of hiding and avoiding capture that would make the Al-Qaeda jealous.

Hang on for opinions from someone that actually knows what they are talking about.

JHAP
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"My mind is a raging torrent, flooded with rivulets of thought cascading into a waterfall of creative alternatives."
...Hedley Lamarr (that's Hedley not Hedy)