im thinking about digging out a pond, while researching, i think i've seen some stuff about "raised bed" ponds.

Hi
Have used that method since 82. Using stacked 4x4's
It's 5x10 around 18 inches above and another 2 feet underground.. I just spread the sand around the yard that was removed. Only trick is to get the first course level in all directions. I originally built this as a container for rainwater but quickly turned into a water garden I used a fiberglass tarp for a liner which lasted until 02 and was replaced with another. Some rot has started on a couple of edges but is still holding up
Very simple and cheap way to build an above ground.
gary

Here's a plan from S Fl.

Here is a link that might be useful: pond

Koi need a lot of run and GREAT filtration, I think that for koi the pond has to be at least 3-4 feet deep so they can get excersize. Also if you hvae a koi pond you probably would not want you dog in it.