I went to the pool store this morning at 9:30 am, I had shocked the pool yesterday at 4:00pm with the 5 gallon jug of 12.5 Liquid Chlorine.This morning's numbers were :

FCL 0 !!!!!

TCL 1.7

CC 1.7


pH 7.8

ALK 99

CYA 70

There is no visible algae in the pool , pool is crystal clear , what in the world is using up the chlorine ?? the skimmer bakets were cleaned , filter backwashed , before I shocked and 15 hours later , NO CHLORINE ??? Of course the pool store did a phosphate test , but that too came out negative .
Pool store suggested I shock tonight with TWO 5 gallong jugs of 12.5 , is that gonna do it ???
I need help !!!!!!!!!!