Among the plants I've purchased are the 4-leaf clover (it's a FERN!!), parrots feather, and bloody dock (plus a couple of underwater ones, but can't recall their names: one has long, slender, flat leaves, and the other is bushy). While waiting for the pond to be ready, went ahead and got my 100 gal. Rubbermaid container and set it up with a small pump and a few goldfish. So far, all is well and the plants look good, and the 2 lilies I got from LOWES a while back are taking off like crazy.
Curious, though, I found a local "aquatic" plant store. Went by there the other day. They had HUGE "beds" of water lettuce and water hyacinth set up as, I guess, a floating filter for their koi tanks. I asked if they were for sale (yes), and wasn't the water hyacinth a banned plant in the state (girl kinda stuttered around then called another employee who "explainded" that they weren't banned as long as you didn't put them in open water. Say what?). Well, water lettuce is also banned for sale, but I didn't know it and bought a bunch of them -- oh well, I do promise to be careful & responsible.