I've never bred bettas, but a friend of mine has bred them for over 20 years and he says crowntails are the hardest to breed. I would stay away from them. Breeding bettas can be pretty easy, but you also have to be careful. If they are not ready to breed, the females and males may fight to the death. Make sure you provide places for them to hide if they need to and allow them to get used to each other before you let them in a tank together. Generally, my friend puts the female in a glass container inside the tank so that the male cant get to her but they can see each other. He only lets the female free after the male has built a bubble nest. He's had much better results that way. Always make sure you're observing their behavior towards each other so you can separate them before one gets badly injured if need be.