Jerry, I've had canna and taro in mine in the past and both sent big roots down through the media. I planted them bareroot though. I'm trying to decide now whether to put some taro back. I love the way it looks and since out here we don't have to clean out and shut down the filter for the winter, it isn't something you have to deal with every year. If the drain hadn't leaked I wouldn't have taken it apart this year and it had been 2 years since the last time I cleaned it out.
Right now I'm trying a couple of things, I got a yellow tropical hibiscus, Sun, and it seems (after only 2 days) to be surviving, it even bloomed. Still, I don't know yet if it will make it long term. I also have a split leaf philodendron in there, it has been in the skippy for years and hasn't been invasive. The roots mainly just wind around the base of the plant. Any philodendron would do well. I'm trying a lipstick plant as well, 2 days out and it hasn't wilted. They live normally in the crotch of trees on debris and what I've read they mainly need good drainage, I've found that moving water functions as good drainage. If it weren't so hot out here, I'd try a fuschia. We had to move the one that is here inside though, even with shade and lots of water it was frying. Dwarf papyrus does well and has shallow roots, also dwarf cattail.
Really, the canna was fine except that it needed more sun so it got really tall reaching for the sun, if you have full sun it would stay dwarf. The roots pulled up easily and the new shoots stay close to the parent. If I had full sun, I'd put it back because the foliage is so pretty and it gives a nice tropical look. The taro is just gorgeous in there, it's the darn runners and the small roots that get down into things and then blow up large.
