Possible ICH

Once you already see the infection, it is in the tank. Your best bet is to put the fish back in and treat the whole tank. There is a great article on the salt and heat method if you are not familiar with it, it is really one of the best ways to treat ich effectively!

The chances are at least decent that you have ich in the original tank. I would treat as Holly reccomended. There is always the possibility that you removed all living ich with the fish but as easy as ich is to deal with and as well as it hides why take chances?
Dave

Read David's ich article and try the salt method. Out of all the methods of killing ich, the salt method has worked the best and most consistant of all of them. I've never not killed ich with salt but medications have failed on me more than once just make sure you don't overdose or you might shut down your biofilter. Salt works well because it won't degrade, be removed by activated carbon, stain your tank or lose its strength on the parasite. It is also relatively stressless for the fish. One more benefit or salt is that it kill 9 freshwater parasites and reduces the numbers of other ones. I use salt in all my quarantine practices because of this. Good luck with your fish. Also since one fish is showing spots, chances are that all your fish will have it probably not showing itself because it is hidden in the gills so treat the entire tank.

I have a red tail shark who barely noticed 10 teaspoons per gallon when I accidentally overdosed. This guy is supposed to be a sensitive fish.

rrkss is right. I followed his posts on ich and read the articles doing both the salt and medication route (i have two cories and they were fine). The ich was gone in a week and no fish loss. Best of luck...be sure and get that temperature going up to 82-86 degrees gradually. That is the key.

My overdose on salt shut down my biofilter for only two days. I tested today and my biofilter is up and running with perfect water quality again so salt is less harsh on the bacteria then using something like formalin which is also caustic to fish. Temperaturewise, the highest I would go is 82*F. I had it at 88* but lowered it to 80* and my fish are looking a lot better. 10 days of salt will cure ich at 80*F with little to no stress on your fish.

I just got rid of ich in my tank with the salt method. It worked great ich was gone in 10 days. I have changed the water in my tank once and I will be doing it again tomorrow to get all the salt out of the tank. I had my temp at 82*.