i am sure that you know this but have to say it for those who may not know. when treating with meds, you need to remove the carbon in the filter or it will remove the meds from the water. meaning you may as well flush them down the toilet.
also salt is good to add when treating fish for disease. aquarium salt aids fish in the proper function of their gills. when fish are sick and diseased their gill function can become handicapped. fish use thier gills to remove toxins form thier bodies. when their gills are not functioning properly, the toxins build up in their bodies and can lead to fish loss. the dosage of salt is one well rounded tablespoon per every five gallons of water. when replacing water for water changes it is only neccessary to add the proper amount for the replacement water, not the whole tank again. also scaleless fish will have to be removed as aquarium salt can burn them.
semper fi