Betta fish are sensitive to changes in water chemistry, and adding salt can upset their delicate balance. It can:
* Increase the salinity of the water, which is harmful to bettas.
* Cause skin irritation and stress.
* Interfere with their ability to absorb oxygen.
* Lead to health problems like fin rot and infections.
Instead of salt, focus on providing clean, dechlorinated water that's the correct temperature. You can use a water conditioner to remove chlorine and chloramine, which are harmful to fish.
If you're concerned about your betta's health, consult a veterinarian or a knowledgeable aquarist. They can help you determine the best course of action.