Another small point on the tank cycle. It is not needed in my view as there is very little load as well as the fish may not eat anyway. Feeding sick fish is often a waste of time and only creates a problem. Second is that I feel one of the best meds is clean water. That means many times, I will be doing very large water changes which keep the ammonia down even without filtering. Some meds specify doing water changes between dosing. Third is the way some meds work on the bacteria. You might start out cycled and the med kills the bacteria so no need to start out cycled!
I keep a dry tank, bottom painted black, and keep a small filter handy. I fill it with water from the tank the fish is in to avoid a shock and then certainly keep it heated to whatever temp is recommended for the disease. I add decor for fish to hide depending on the type fish.
When breeding, I kept a small filter cycled to swing over but I left the tank empty. To prevent passing disease on from sick to fry, I always did a bleach soak of all the equipment if it had been used for QT.