Undergravel filter, other filter, live plants, and a stock of the following
1: 3 ottos
2: Some smallish easy fish like zebra danios
3: And maybe a single 'feature fish' like a gourami
all in a 20 gallon tank that costs 40$ at Wal-Mart, it should be relatively low maitinence, just once a month cleaning, should be fine.