Why do bettas swim sideways?

Swim bladder disorder can cause bettas and other fish to have a problem swimming upright. This may be a sign of a larger issue.

Constipation is the leading cause of swim bladder disorder. The intestines become inflamed and press on the swim bladder. The swim bladder is a small organ that fills with gas to help fish maintain buoyancy. When it is pressed, it cannot fill with gas correctly to keep the fish stable.

Feeding a fish a proper diet can prevent this from happening. A bacterial infection can also cause swim bladder disorder. If the problem is not corrected quickly, it may cause the fish's death.