I have had a lot of replies,and i thank you.However i am not sure i got my answer.
How long to quarantine a newly purchased healthy eating no visible health problems fish?
If its 6 weeks why.Why should you treat a fish that doesnt look sick.
That is a question that only you can answer as many will say a "passive QT" is sufficient and if no observable disease is present then in the DT they will go. Others will say that only an "aggressive QT" can assure that the fish is disease free once sufficient time in proper medications has occurred.
Here is an article that may help you decide:
http://saltaquarium.about.com/od/diseasequarqt/a/aaaggressiveqt.htm
Passive Quarantine (six weeks):
•PROS:
•Time tested method of detecting problems.
•Less invasive (Treats only detected problems).
•Less expensive (not buying unused treatments).
•CONS:
•Takes six weeks.
•May not expose potential problems (latent external/internal parasites).
•Does not treat potential problems.
•Potential wait for proper treatment after it shows up.
Aggressive Quarantine:
•PROS:
•Short (approximately two weeks).
•Thorough (treats most potential problems).
•Less likely to pass a problem to your show tank.
•Takes full advantage of a Fast & Cheap QT.
•CONS:
•Potentially higher cost (purchasing a number of products).
So, with that said, what do I do?
IF I purchase a fish(es) from a quality operator such as Diver's Den where the fish are observed and expected to be disease free then I will QT for about two weeks for observation to confirm what I expect...a disease free fish. But during this time if I observe something unusual in a fishes behavior or physical issue then it is aggressive QT for 4-6 weeks. It will be aggressive QT for fishes from other suppliers (such as Live Aquaria's LA operations/or Blue Zoo) since the same observation and quality control as at Diver's Den does not take place, so it is up to me to be more than sure.