Fish do have feelings and can become very stressed. However, betta fish have simple needs. If your fish has enough space, lots of hiding places and the right care and diet, it should be happy. A happy fish has a good appetite and plenty of energy. Watch out for the signs of stress, and if you see any, determine what the problem is.
Provide a large enough tank if you haven’t already. Betta fish can survive in small bowls, although not usually for very long, but these environments are difficult to maintain and chances are high the fish will become stressed. A betta fish should have at least a 10-gallon tank but the bigger the better. Provide plenty of aquatic plants and rocks to form hiding places.
Observe how the fish eats. Happy fish have good appetites. They will be especially excited by live food treats such as daphnia -- water fleas.
Watch your fish’s behavior. Momentary agitation, for example the fish swimming very fast if somebody makes a sudden movement in front of the tank, is probably not a problem. The opposite, lethargy, is. Stressed betta fish often become very slow moving and may even appear to lie at the bottom of the tank.
Examine your fish’s physical condition. Stress makes fish vulnerable to physical diseases. White spots or drooping fins mean your fish is ill. It needs the appropriate medications, available from pet supply stores, and crucially an environment that won’t make it stressed. Determine the cause of the stress, perhaps a move to a new tank or the introduction of another fish, and rectify it if necessary.