3/8" diameter airline seems pretty typical for the fairly short runs inside ponds. The longer the run, the bigger diameter pipe you need to keep drag./friction/resistance reasonable, and the flow rate high enough with typical aeration system compressor pressure. The situation is directly analogous to the need to use larger diameter wire for long distance electricity transmission to reduce the resistance and hence line loss (Mechanical Engineers and Electrical Engineers even use the same symbols for schematic diagrams of pneumatic/hydraulic and electrical systems - or at lease they did 40 years ago when I was in school).


"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
[Linked Image from i.pinimg.com]