All that said (and I'm a big fan of siphons), if there isn't much elevation difference between upstream and downstream, they can be really frustrating.

Another tip, it is probably a good idea to generally have some larger screen over the pond side entrance. I've done it both ways. Sucked some nice fish through an 8" siphon that didn't have a big (covers big area like a cage not just across end) screen around end. I've also sucked a turtle against a 4" siphon. It both killed the turtle and stopped the siphon somehow.

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