Friends betta is having bouyancy issues, they said it’s a common recurrence for swim…

Friends betta is having bouyancy issues, they said it’s a common recurrence for swim bladder issues. For a long time the fish hasn’t had normal swimming patterns, sinks easily and relies on support around the tank. Betta has begun to lose color and turn white/grey around the face. No fuzz or growth that I can see and he is still excited for food and interaction and seems to be in “good spirits”. Not sure what to do to help, friend says she cannot afford a vet for a fish. Water specs are all normal. 10 gallon tank with heater and what looks like a sponge filter. 2 snails that are totally fine and normal.