I would hold off on buying that system until you hear from the experts Ken. I'm certainly not one of the experts but from what I've read here I do know that it takes about one half of one PSI (or .5) psi per foot of water depth to push air to the bottom. So at 18 feet deep the compressor would need to have enough air flow at 9 PSI to run a bottom diffuser. Also from my reading my understanding is that soaker hoses work ok in shallower water but are not as good in deeper water. A nice bottom diffuser would probably work better in the deep part of your pond.

What is the basic shape of your pond?

Hang on and I'm sure one of the experts will give you good info (as opposed to my ignorant speculation).

JHAP
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"My mind is a raging torrent, flooded with rivulets of thought cascading into a waterfall of creative alternatives."
...Hedley Lamarr (that's Hedley not Hedy)