Multiple Filters/Excessive Filtration Increases Stocking Density?

People do grow plants in pots successfully, including Diana Walstad. You do need to put in a decent substrate, again I will use soil but you could obviously use one of those special (= expensive) plant substrates. I would use ordinary traditional clay flower pots (unglazed). They're only made of pure baked clay and should be as safe in an aquarium as anything else I can think of. I understand that you would have to repot the plant with new substrate, and probably divide and reduce the size of the plant, about every two years, which isn't very different from any ordinary potted land plant. A 15 cm diameter pot should be enough for a really big Amazon Sword, or a good sized group of Sagittaria, for instance. In fact, a considerably smaller one would likely suffice. A wider shallower one is probably better than a tall narrow one. A plant in a pot will also, of course, be nearer the lights which should help growth.