I am going through the same issue. I have been fighting this battle for 3 years now. Everyday I vac the pool and by the next morning I have the spots in the depressions of the liner. They look greenish in color. They vac easily and will dissipate if I brush them. I keep my levels right where they should be. I have done the overnight chlorine test and that too is fine. I added sand to my filter this year to bring up to the proper level as all the backwashing last year I lost a bunch. I was hoping this would help but it has not. I am at a loss as to what this stuff forming on the bottom of the pool could be. This is very frustrating as all my test and levels are indicating there is no algae in the pool but these spots show up every morning.

Well, if my guess is correct, and my situation is the same as yours, then the problem is inside the filter. I am not sure what your innards look like on your filter, but I think mine must have a small crack in the tube/pipe that leads from the bottom laterals up to the top of the filter where it then exits to the pool return.

I just tried putting 5 cups of DE on top of my sand, thinking that the sand was not trapping the "fine silt" and my only conclusion is the pipe. My pool is clean during the day until I turn on the filter.

On a plus note, my water is very clear now that I put that DE in trapping the small micron stuff!!!!

I seem to be having the same problem for the past 2 weeks. The greenish tinge puffs up like a cloud even when I just plonk the brush in the water,i.e., it brushes off fairly easily. Between my husband & me, we have been testing the water everyday now, brushing 1-2x/day, tiger shark running 4-8hrs/day, pump running 12 hrs. My numbers have been good (2-week range): FC 3-6, CC=0-0.5, CYA 30, TA 80. Even w/ shocking 2x (passed all criteria), the "dust cloud" just comes back. Should I just shock again, raising it to mustard shock level this time?

If you passed the OCLT, it's probably just dust.

Yup, passed the OCLT 2x.
And surprisingly, when we had rain 2days in a row, the pool water got crystal clear. Is that another indication that this could just be dust?
I'm at my wits end!

I am battling this as well, but have made significant gains this week. I have placed 2 skimmer socks in my skimmer (not sure how inground systems work, so this may or may not be possible for you). I rinse them several times per day as they are really trapping the gunk. I also throw a pair of pantyhose in on top of those two skimmer socks when I vacuum for an extra measure. Last week I had this silt spread out over the entire pool...enough that every pass with the vacuum left a visible 'clean' path. Each day has been getting better, the water is now clear and sparkling. Today when I went out, there are just a few little random spots.

My problem is stemming from a filter issue that is allowing dirty water back into the pool during vacuuming... and while I haven't solved that issue, attacking the problem from the other side of my filter (at the skimmer) has proved to be working for me. I have a sparkling pool... and that is what I wanted. This approach may work for you too.

I've used the skimmer socks during opening, but will begin following your tip here dattia, to see if that helps. Thanks for suggesting it!

I am having a similar issue as the person in Okla. I am in northeastern Okla. What is DE? Is this similar to sand only coarse?

I think I got it. Media that goes in a DE filter system

Yep, you got it. It's Diatomaceous Earth.