I've never used that specific med so I'm not sure what it will do to your plants or shrimp. You also may have to remove any carbon if you run it in your filter media.
If possible for you, it maybe worth getting a 10 gallon tank with air stones or a cheap hob and a heater to put him in for treatment. It doesn't have to be cycled. Keep it bare bottom, feed every other day and test the water daily. Prepare yourself for frequent water changes and med dosing.