[Split by moderator from what-is-this-brownish-dust-at-the-bottom-of-my-clear-pool-t35509.html - Please do not hijack, but instead start your own thread. Thanks, jblizzle]
By 'trial and error', I have come to conclude that the fine brownish dust at the bottom of the pool seems to be triggered by the water coming from the inlet with the pump running consistent with the run53's observation. Whether it is anything coming with the water, I do not know. So when I used a pantyhose to filter this inlet water, the brown dust does not come up. The next day, I remove the pantyhose and as expected fine dust appeared. I use the pantyhose to find out what fine solid material comes with the water but when I checked after running the pump, there was nothing in it. Now I think that perhaps the rush of water from the inlet without the pantyhose filter triggers some reaction on the pool water that generates this fine dust as a pantyhose reduces the water pressure from the inlet. Then again I would not expect to see any dust if there is no water pressure, that is the pump is not run. At least for now there is no fine dust but I am now concerned with any ramification of the pantyhose fix. When I vacuum the fine dust using again the pantyhose as receptacle, I fine dirt and some fiber-like material. Just wondering if this comes from the pump filter. Anyway, hoping this triggers some investigation to get to the bottom of the issue.