My boyfriends had a 10 gallon tank running for about 3 years now. He does a water change every few weeks, and tosses in some shrimp pellets every few days and other then that, it's pretty much good to go.
His setup is a standard wallyworld 10 gallon tank, with 2 13 watt PC bulbs in the hood, and a sponge filter. Miracle Grow Organics Choice Potting Mix, under a mix of pea gravel and eco complete. He planted it with a few kinds of crypts, bolbitus, java moss, anacharis, and duckweed. About a year and a half ago, I gave him 4 cherry shrimp to start his colony off with, and now it holds pretty steady at about 75-100 shrimp in the tank, with little to no effort on his part. Low care, easy, and inexpensive. I go through and thin out his plants for him every year or so, but otherwise he just lets it run free and jungle up as much as possible.