Yes, you can put a betta fish in tap water right away. However, it is important to treat the tap water first. Tap water may contain chlorine and other chemicals that can harm the fish. Use a water conditioner to remove these chemicals before adding the fish. Additionally, make sure the water temperature is suitable for the betta fish. They prefer warmer water, between 76°F and 82°F. Test the temperature and adjust if necessary. It is also important to provide a properly cycled tank with a suitable filter and decorations for the fish to thrive. Following these steps will help ensure the betta fish's health and well-being.