Had a little bit of algae in the pool, CC=0.5. shocked to CL=18 with CYA=50, overnight CL loss was 0.5 with the very first testing. So I let the CL drift down. On next testing, CC is still 0.5 with normal within range CL level. Brought CL back to 18, brushed pool better this time. let CL drift down to normal range again. test: CC 0.5 again. Is there still algae in the pool? What am I missing? Water is sparkling clear.