Since I will not have peat laid down over thousands of years, I guess I'll have a slightly basic-pH, hard-water wet depression, but a fen sounds so much more interesting:) Thanks for posting this info! Any ideas for unusual plants that we can add is appreciated. Not sure how I might contour a 30' diameter area to build something that will host a diversity of flora and fauna. It will likely be a dead end off the drain channel from the artesian pond overflow so it will not have any flow-through, but it could. I could also add some old wood chips to line the bottom if that might help the system mature faster.