Any time I treat fish in my sick tank I always break it down and clean and sterilize everything with a bleach solution once the fish go back to the main tank. Then I will run the filter in one of my other tanks to build the bacteria back up and keep it going until I need it again. Then when I need it I just set the tank up... fill it with water from a healthy tank... add the cycled filter... good to go. (Just make sure you rinse everything really well to get all of the bleach out, and use chlorine remover in the final rinse water)
I wouldn't move the cory back with the others until the full treatment is finished. Then I usually give it a few days after that to watch for relapse... incase it wasn't all gone. It is like the doctor says... finish all the medicine even if you are feeling better... it will probably act better before it is all better.
I wouldn't move the cory back with the others until the full treatment is finished. Then I usually give it a few days after that to watch for relapse... incase it wasn't all gone. It is like the doctor says... finish all the medicine even if you are feeling better... it will probably act better before it is all better.