I have some 3/4" PVC left over from an irrigation project, and I'm thinking about using it to get the air to the edge of the pond, then going with weighted tube in the water, UNLESS ;-) someone convinces me that running the PVC in the pond is a good idea. I'm thinking it isn't.
I used 50' of the sinking from the diffuser back towards the bank, then used 3/4" black water pipe. This allows me to pull the diffuser out of the pond or relocate it without disturbing the portion of the 3/4" black plastic pipe that is weighted down with concrete blocks.
"Next time" I would probably bite the bullet and go with all sinking within the pond. The 3/4" water pipe works fine above water.
Even after weighting the pipe down every ten feet or so, it still floats up off the bottom between weights a few inches. Looks like something waiting to snag a fish hook to me. But it did save considerable money in my 3 acre pond using a good portion of non-sinking line. It works, but sure is not as simple nor neat of installation. If you can afford it, go sinking for everything in the water. If not, try to use at least the last 25' or so attached to the diffuser sinking, so the diffuser can be raised without disturbing the weighting system (however you choose to do it) on the remaining pipe.
That is my experience with three double diffusers in a 3 acre pond and two single diffusers in my sediment and forage ponds.
