In the name of accuracy, that post should probably read "about 10 years or something". It was a year or two ago I ran across that story, and I don't remember the exact time it took, I just know it was a good while, with verrry gradual salinity change. I don't know what fish they were or even where I found the story, but it must have been at least a fairly reliable source, else I wouldn't have believed it myself
If I got REALLY lucky maybe I can find it again.
Maybe you could try a similar experiment, DrFish, and see what result you come up with?