echo's losing his mind... the sand at lowe's was 5 dollars for 50 pounds.
don't pay five dollars a pound for anything that you're going to be putting into your aquarium as substrate or decoration. as far as fish go, well that's a horse of a different color. =)
the sand we picked is some kind of medium mason sand... we liked the grain size of it, play sand seemed a little too fine.
and bigred... sure, nobody needs to manually stir up the bottom in any outdoor body of water, but streambeds are getting stirred up naturally by water currents, lakes and ponds by human swimmers and a lot of the animals that make their home in or near the water.
also, the hugeness of such water bodies would allow one to have much more leeway in regard to little nasties and anaerobic bacteria. an inconsequential amount of such things in a pond can be an excessively lethal amount in a home aquarium.
i don't think it's worth too much worry (certainly not worth uprooting your plants), but if you have an unplanted area in the tank, surely it can't hurt to give it a little stirry-stir. although you're probably correct in assuming that your cute little mustached renegades are taking care of that for you. *SUPERSMIL