They would help control any snails and associated parasites.

I can't imagine they would do any harm. They would take up some of the carrying capacity of the pond but unlikely for many if any of them to get large enough to escape the gape of a blue.

So in my non expert opinion I don't see what they would hurt and they might help with the parasites. But then I have a fondness of the cuddly things so am biased.

John

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