Day 97 update: Almost 100 days later, my PB Tang is finally in her new home - a 150 gal mixed reef. She's survived Ich, a 12 hr move, and living in a 30 gal tank (then sterilite container) for all of that time. See pics below!
I guess it all depends on the half life in the fishes blood. In humans it ranges from 6 to 50 days from what I just read. Therefore the minimal time for elimination will be around 1 month, and max would be over 8 months in some individuals. that is just for one dose. Not sure why the big range, but if the same is true for fish, oral ingestion has possibilities.
I had a tank that I thought was free of ich for over 3 years. Never added a fish, but after a power outage and a temp drop it came back. The only way to know if you are ich free it to use your tank water on a highly susceptible fish. Sorry, but for good reason I'm skeptical.
CP definitely works when added to the water. It is tough to find though. QS is readily available and also is very effective. I have just found it to be tough on the fish. I have used it in my fish only display that houses a skeletor eel. All of my fish including the eel refused to eat for 2 weeks and my spot fin butterfly had very frayed fins. The ick never returned.
There are some legal issues that I believe are preventing it. For a small company, side business with not much to lose, it might not be a big problem to get shut down for doing something wrong. Big company = big fine and problems if there is a violation of the law. much more to lose.
I'm not sue if it is OK to sell CP without a script. My understanding is that one is still required, But I do know tha drugs like accutane, Prozac and Viagra needs scripts and can be readily purchased online without one.