OK, there are 2 stages to this: killing the algae, and cleaning up the algae. Is the algae dead, yet?
(Dead = blue, blue-gray or gray water with NO green PLUS no green when you brush or vacuum)

Also, I haven't seen a full set of test results yet (FC, CC, pH, TA, CH, CYA). Can you post the most current readings?

Finally, what color is/was the sediment you had, and what color is your backwash discharge?