Beta fish can live in tap or bottled water. If you are use tap or bottled water, ensure you buy a bottle of Water Air Conditioner for the Beta. Make sure it says: Beta Water Conditioner, or on the bottle it says it can be used on all types of fish.
Betas originally live in hot climate of south east Asia in mostly stagnated water like mud puddles to rice parties. The fish can be kept in a relatively small sized tanks due to having abilities to retain oxygen inside their gills much like a scuba gear. Do not use fresh tap water. Always do a 25% max. Of water changes. These are very hardy fish and top of the line male bettas can fetch around $20 per fish!