Geez... Lotsa questions and advice!!!! I'm really happy to receive BOTH!
Here's where I'm heading.... The purpose of the pond is really aesthetics. I love the look of water and the sound of it falling...
The pond will have a liner. The soil is VERY sandy (ultra fine) so I'm hoping it wont need a pad under the liner.
The entire contents of the pond will recirculate through filters about every two hours.
(Lots of pumping and filtering )
I'll probably throw a dozen or so goldfish in there. They can grow to 20 pounds or so if they're not eaten first. I will try to trap and relocate the local raccoons, but I'd welcome a heron (they're so damn beautiful) I've come to terms with the deer foraging through my small orchard so a heron seems like small change.
I didn't expect such interest, so I'll keep posting as work progresses.
Here's the filter I'm looking at. Anyone ever used one of these? If so I'd like a review before I throw away my money...
http://www.123ponds.com/a50300.html
If you put down a liner, also consider putting some crushed stone around the edge. This will keep the fish further down in. AQ Heron will walk up to about his knees in water, and if you have a bare liner, the fish will come up to the edge, and the Heron will ****** them up. Believe me, a Heron can carry quite a bit of weight. Maybe that's why some people call them cranes

Also raccoons will grab the small fish.
And if you see ANY cattails starting, get rid of them ASAP because they will take over. And don't plant any bamboo. A friend of ours gave us a couple Water Iris for our pond and it had one or two small roots of a short bamboo plant. Or ground is clay and a backhoe has a hard time digging. THe roots; of that bamboo came into our about 10', and grew up through the ground about 4'. If any bamboo get started, it will poke all sorts of holes in your pond liner.
As far as an underlayment, I mentioned old carpet, and you can get all you want from carpet places. Heck they may even pay you to take it. But if you don't want to go that route, lay down a layer of sand AFTER you rake or rockhound everything out of where your liner is going to be.
You can plant ornamental water lilies, but keep them in a pot. Usuall a shel is made around a pond for potted plants.
When it comes to your filter, I probably wouldn't put one in like you are looking at, but what you can do is get a couple 300 gallon Rubbermaid tubs and fill with lava stone and water hyacinths and it will filter your water great. Set one tub for a water falls, and another tub higher than that one, that the water will go into the tub below it. You want your pump set so that the water goes in the bottom of the top tub, overflow into the next, then overflow into the pond. There used to be a nursery south of us that was into water gardens, and he had his set up this way, and his water was crystal clear even in the dead heat and drought of summer. And if you recirculate your water enough, you won't have algae. If you have access to large rocks or boulders, use them in you pond as much as you can. This gives the small fish a place to hide. And if you really like to hear the water, have a water falls that is built out of stone, but is hollowed out behind the falls. This allows the water to echo back, or magnify the sound.
Another good site for ponds is Garden Web. The first one is their pond forum, and the second one is their pond Gallery.
http://forums2.gardenweb.com/forums/ponds/
http://forums2.gardenweb.com/forums/ponds/nph-ind.cgi?type=gal
Good luck with yours and make sure you keep us updated


I know that whatever you do, it is going to look great.