This usually means sediment, which on a well often means the screen or the pump setting rather than the water itself.

A well that draws from too near the bottom, or past a worn screen, pulls fine sand along with the water, and that sand ends up in every aerator and valve downstream.

Look for grit in the aerator screens and the bottom of the toilet tank, worse after heavy use or a power cut, and taps that gradually lose flow.

Do not buy a fine cartridge filter first. Too fine a filter on a well that is actually making sand blinds off in days, and the pump pays for it.