Andy Hill wrote:

Air pumps are basically for looks

We have all seen fish die if an aquarium pond looses its aeration, so
they do work. They need to be sized to the pond. They have ratings on
the side of the box for different sized ponds. Warm water doesn't hold
much O2 and may need more aeration. The air pump for my pond cost
nearly $200.
--
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18,000 gallon (17'x 47'x 2-4') lily pond garden in Zone 6
Cheers, Steve Henning in Reading, PA USA