I cleaned and changed the water in my betta fish's tank yesterday (added neutralizer and de-stressing salt), and put the fish in this morning to ensure that the tank temperature and temperature of the container he was in would be the same. The fish, however, seems to be unwell. His eyes are bulging a bit and he's more sluggish than usual. He alternates between swimming around and settling at the bottom of the tank with his fins clamped to his sides. Also, he seems to have lost his appetite.
Any advice would be appreciated. Thanks!