Phil in CA. Pond depth where diffuser/diffisers are located is important.
Long airline runs deal with at least three variables; pressure, air volume, CFM and tubing diameter. If you are using a low pressure 'pump' then pressure loss becomes important because you want enough pressure when finally ariving at the pond to continue to push down to the bottom and release air. From your post I assume you don not have a compresssor yet. Two main options.
1. Low pressure (10 psi) high air flow (4.5-5 cfm)rotary vane pump 1/4 to 1/3 hp will work but you will need 3/4" airline run to the pond. Then under water you can go to 1/2"-5/8" (5/8" ID better) . 1/2" is only good for abt. 400ft. before you start to lose psi. due to long tubing distance.

2. Higher pressure pump 20-50psi. Piston, diaphragm or roc-r-arm. All are noisier than rotary as Hondo above found out. He wouldn't have heard the rotary upstairs. 100psi is too high not needed. Plenty of excess pressure for pushing air thru small tubing 3/8"-1/2" for 600 ft. , but low cfm and thus fewer bubbles. Fewer bubbles means smaller diffuser and maybe only one diffuser and quite a bit less water movement.

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