Took 3 weeks to get crystal clear H20 after pool was opened 7/3; drained almost half of H20. Pool sand was replaced August 2019; ph, alkalinity, FC all ok, stabilizer slightly high, hardness slightly low, no TC measuring. Water crystal clear. No sediment on floor when pump/filter are off but when circulating, constant build-up of black "dust" collects on pool floor. Vacuuming to waste several times daily and adding fresh H20. Yesterday added gel clarifier to pump basket to "coat" inside of filter. Backwashed/rinsed. Continual problem for 3 weeks; nothing works. Put 3 phosphate tabs in skimmer 3 weeks ago. What can I do? I am at my wit's end. This pool was my hubby's baby and he passed away; I'm 75 and finding it very difficult. Can anyone help?