My betta fish has lost his energy, his colors are dulling and his fins have thinned (they look like sticks). He still eats normally and doesn’t show anything other big syntomes. What do I do?
PS. I have added before and after pictures
You should change the water and make sure the water parameters are fine for your fish
I leave you this link with a lot of information about how you can look after your betta fish.I hope it can useful for you.