It is reccomended that you cycle your tank for at least 7 days before adding any fish. Even then, you must base your purchase on hardiness, not beauty. a beautiful fish will most likely die because of the benifical bactieria has not yet multiplied enough to consume the harmful ammonia and nitrite still present in the water after 7 days. Also, NEVER add medication to the water of your tank! adding meds will kill the benificial bacteria and the bacteria will take more time to re-establish itself.