* Water conditions: Check the water quality to ensure that the temperature is correct and the pH level is between 6.5 and 7.5. Also, make sure that the tank is clean and has plenty of hiding places.
* Diet: Feed your betta fish a high-quality pellet or flake food that is specifically designed for bettas. Avoid feeding your fish live or frozen foods, as these can introduce bacteria into the tank.
* Other fish: If you have other fish in the tank with your betta, make sure that they are not aggressive towards it. Bettas are territorial fish, so they may feel stressed if they are constantly being harassed by other fish.
* Stress: Bettas can become stressed for a variety of reasons, including changes in their environment, loud noises, or even seeing their reflection in the glass of the tank. Try to minimize stressors in your betta's environment as much as possible.
If you have checked all of these things and your betta fish is still lying down, it is best to take it to a veterinarian for further examination.