Go to a pond and take a handfull of the mud at the bottom. Put it in there with some old aquarium water and ID all the amazing life. Freshwater live rock, I call it.
My Betta is in a 2.3g tank & loves it more than when he was in the 29g plus he's become very tame. I just do a 30-40% water change once a week (tanks filtered) & never had any problems