You can use regular tap water as long as it is dechlorinated.
Optimally the water for keeping healthy Bettas should be soft, warm, with a neutral to slightly acidic pH. Bettas may be kept in a community tank if no aggressive or fin-nipping fish are present. However, only one male may be kept in each aquarium, unless they are separated by a barrier. They will eat flake food and should occasionally be fed some type of freeze dried or live food. Good luck!