Yes, if you do a partial water change, run carbon for several hours, then remove it, and re-treat. However, if he is not substantially better, this may be the wrong medication for what ails him. Usually, if you have chosen a medication correctly, a fish should be substantially better, almost well, in 3-4 days. With bettas, make sure the tank has had a partial water change, and is warm. They do need heat - 78-84 degrees. To medicate, you also have to have a filter.
Date published: 2016-09-21