They don't need a cycled tank but it's a good idea to cycle it anyway. If it's not cycled, you'll have to do 100% water changes every week. I have a betta in a cycled 5 gallon and a betta in an uncycled 2.5 gallon and trust me, the 5 gallon is 10x easier to manage.
P.S. what size is the tank?
