Betta fish in a 3 Gallon tank?

use distilled water from the store, use gravel. plants help the fish hide and not feel stressed out(get plastic ones from petco,or natural ones as the fish can nibble at it). my last betta lived for 2 or 3 years and i didnt use a heater or filter. just clean the tank when its dirty. ( transfer the fish into a bowl of room temp distilled water,then clean the tank and replace the old water with new water). room temperture water is good, but in like alaska or where its really cold use a heater.