OK....here's your list:

1. plan on 250 to 300 gallons per fish with a 1000 gallon minimum size.

2. plan on 36" deep or deeper....deeper is better.

3. plan on some shade structure...shade sails are nice and not very expensive. In zone 9, that water will get pretty warm with no shade.

4. no rocks in the bottom!!

5. aerated bottom drains that gravity feed a settling tank and bio-filter, with a pump return to the pond.

6. Skimmer

STUDY STUDY STUDY before you start digging!! Koi Shack is a good place to study up on the specifics of koi ponds.

Here is a link that might be useful: Koi shack