This question came up a week ago, I haven't checked back through that thread but there might be something not mentioned in this one, here's the thread link: http://www.tropicalfishkeeping.com/a...-plants-36229/
Also, I commented on potted plants yesterday, I'll just copy over what I wrote as nothing further has been posted there. This is just a caution to ensure there is adequate water circulation if you go with plants actually in pots within the aquarium which is sometimes necessary as 1077 points out.
But one caution on potted plant roots: the water must be able to fully flow through the roots of plants. It is essential. There is a host of aerobic bacteria living in the substrate, and their main supply of oxygen is from the water passing through (same as water flowing through the filter to bring oxygen to the nitrification bacteria or they will die) and the plant roots. Plants during photosynthesis produce oxygen, and some of this travels down to the roots and dissipates into the substrate to provide oxygen to the bacteria. Plus the water must be kept flowing through the roots to bring them nutrients. All nutrients come from the water. The liquid fertilizer you add, the substrate tabs or sticks that dissolve into the water, the minerals in the water from the water changes and fish food and waste broken down by those same bacteria down there--all these must be brought to the roots via water flow. This is why I prefer small gravel substrates with the plants in the gravel. It is all but guaranteed to work the way it should--and must.
Pots can work, yes; just make sure you still have that essential water flow. This was one good aspect of UG filters that we all used years ago [there are other detrimental factors which is why they are not so common now], and it was the basis behind the move to substrate heating cables back in the 1990's, to create convection currents and keep the water flowing through the substrate. But all that has been shown to be less significant now because the water flow in a biologically balanced aquarium is adequate with the bacteria, healthy plants, and fish.