No worries...
Just becareful on the dosage when you add the medicine to the bn~
While you are isolating the bn in it's own tank, place some food for it to chew on...a slice of cooked zucchini / broccoli / cucumber would be great for the bn, or you can place a small piece of algae waffer for it nip on.
For the preparation of the vegetables mentioned above, just simply slice a thin piece of zucchini / broccoli / cucumber, boil it until it soften...then place it under tap water to cool it down and place it into the bn's tank. (If you don't cook the vegetables, they won't sink~)
Oh..one more thing that you need to remember is to add a little bit of salt (aquarium safe) to the tank everytime when you do water changes. This can restrict the growth of a wide range of bacteria / parasites, thus preventing development of diseases.
Anyway, good luck to your bn and hope it will recovery very soon~ Cheers~~(^^)p