You might want to go to your local nursery, if they have water plants, and pick thier brains on how they manage theirs.
I have been experimenting with various water plants. I have plants in gravel, some in soil, some anchored by rocks both in and out of water. I have discovered that some, so called water plants do better in dirt next to the pond. I don't use any chemicals in my ponds for the plants or water quality, everything is as natural as a home made pond can be.
I have plants in tubs without fish and I have found that some do well and others are doing better where there are fish to fertilize the water.
Hope this gives you some ideas.