Interesting read Pollopicu. I recall this:
“…look for fish sauce with a clear, reddish brown colour, like the colour of good whisky or sherry, without any sediments. If the color is a dark or muddy brown, the sauce is likely to be either a lower grade, or one that is not properly or naturally fermented; it may also have been sitting on the shelf a bit too long. Good fish sauce also has a pleasant aroma of the sea, not an overwhelming smelly fishiness, and should not be overly salty. If the bottle you have been using makes the dishes you cook taste too fishy, try a new brand.”
I must have been buying crap fish sauce. Lesson learned.