no sandbed here but my fish crap a lot so I might as well call it turbidity
PE has always been good (especially with the wavebox) and I had no PE when I had a sandbed (granted, PE was the least of my problems when I had a sandbed). I found when I dosed K I got better colors but I don't remember getting any better PE than without dosing. I'm thinking about taking up dosing again just to see if it does anything.