Welcome Wildblue!

I am in a similar situation as you...I have been designing my aeration system too. I have not installed it yet. Going to the hardware store after work to get more supplies.

If you do not want electric at the pond then you are with the norm of burying airline instead of wire. I think you will find that most will recommend 1/2" to 1" ID air line so that more diffusers can be added without retrenching and adding more underground line. I am putting three 1/2" lines from my little pump house to the waters edge for each of my diffusers so that the control valves are not out in the weather, then using 5/8" weighted hose out into the water.

If you can throw a little more money at the project, I suggest you consider adding another diffuser or two in the shallows for winter time use to keep a hole open. A 1/4 to 1/3 HP pump should run 3 or 4 diffusers so why not add them. With your pond size, you need to run some calculations to really determine how many diffusers it will take to turn the water over at least once a day.

The RV pumps will not pump into deeper water like the piston pumps, but a good RV pump will get to 10 foot easily. Look into the Gast 0523 pump (for DIY)or Pondlyfe systems that use a piston pump. Scott at Hoosier Pond Pros is a good source for info and products. He is also a member here.

Many will advise putting the diffuser/s in the deepest part of the pond to maximize O2 throughout the pond, but others are advising to put them at the 2/3rds depth so that a cooler area can be maintained for heat relief.

I hope that I have given you some things to noodle around.

Fish on!,
Noel