I would use 1/2"-5/8" ID airline and not give it a 2nd thought.

You might be able to get away with 3/8" but if you ever wanted to move more air in the future you'd need to upsize the line.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).