This was taken here in Bonn, early June, a bright afternoon sun going directly into the water.
This is a pond around a little palace (build by former archbishop Clemens August of Bavaria for his maitress (girl friend) ), which is now part of the university (botanical garden).
The pond was rebuild (cleaned and newly planted) last year.
I assume the fish are from a young breed (it seemed, they were actually hunted by ducks)
No need of a polarising filter.
The colors are very close (feeling: identical) to the visual impression.
What looks like noise is mostly very fine details and air bubbles, blurred by the water or out of focus
(a 100% crop is attached)