First off: Pool is pebble, in ground, chlorine, about 12000 gallons (I think). All chemical tests are within limits according to my local pool shop. 300lbs sand filter.
Lately I have been getting very fine dust on the bottom, where the creeper doesn't reach. I can easily brush or vacuum it away, but it just shows up again the next day. Because of this you can always see a dark and light area on the bottom from where the creeper reaches, and the water is never 100% clear. I was worried one of the laterals had broken in the filter or something, so I emptied it out to check them, but they are all fine. Also put in new sand (regular #20 silica sand), and of course backwashed before using it.
The dust/sand in the pool is extremely fine, if i move my hand near it it just billows up, so I am thinking it is just too fine for the filter to handle and just gets pumped right back into the pool. Also the dust has kind of a greenish tint to it, but it isn't algae, since it settles and forms little ripple patterns on the bottom from the current, just like sand at the beach.
I backwash, shock and de-phosphate regularly, keep tablets in etc. I tried using a clarifier, both an 8oz dose and half a bottle, neither helped. I diluted it with a bucket of water as per the instructions first. At this point I am kind of at a loss, and not sure what else I can try, short of buying and installing a DE filter.
Picture was taken a while back.