Hi Mik!
I have a pond just like yours, no intake, hardly any outlet other than spring and winter. Surface runoff is actualy filtered in a mini strom retention pond to keep sediment rich water from running into my pond directly.
Aeration keeps my pond clean and pretty! The fish are happy, the kids swim in it, it is lovely.
Last year I tried to stop the aerator to see the difference (for scientific reasons of course), the water had an algae bloom within 10 days. It became turbid and murky. The fish were not happy (trouts) and my kids started playing video games again instead of swimming in the pond...
Ted knows his stuff! You can't go wrong! Aeration only has benefits if you do it right the first time.
I like to keep my aerator off when it is hot, so I keep fresh cold water oxygenated, and circulate that water at night when it is cooler.
