I have it in my bog (with pea gravel) and it covers nicely while letting the iris and dwarf cattails and Japanese rush grow through. I pull handfuls out regularly and give them away to other local ponders through craigslist or just compost it, but always tell people to consider it invasive and keep it out of any native waters. I don't let it build up too much, since when I pull it it also effects the roots of other plants it is growing through. It will run freely around a pond, but if it gets into the other pots it may get rooted in and be tough to dislodge without harming the other plants' roots. And you already know what it does in your yard...
Where you are you could also grow Asiatic Pennywort (Centella Asiatica), which expands by runners like strawberries, instead of the continuous vine like habit of the hardy pennywort most of us grow. I think it would do very well potted up and growing in a bog, although I'd keep the crown at about the surface of the water. You'd probably need to winter over a pot of it to make sure you had some to start the spring with if the winter killed it all. This is a long standing Ayurvedic herb and has recent interest from mainstream medicine since it seems that some of the reported uses have merit. Supposedly it is good for high blood pressure, mental acuity, reducing wrinkles, reducing varicose veins, digestive issues and just about any other ailment you can think of. It is used in a popular drink in Vietnam. The leaves look closer to wild violets than like the mini-lotus look of hardy pennywort. You can grow it from seeds or a few places have plants.
Goodness, I just filled a 5 gallon Lowes bucket with some I thinned from our baby bog! I can now at least see some of the other plants I ordered from Trickers. I'm going to have to stay on top of this pretty, but crazy fast growing plant !
