remtom46 writes:

One bag of shock is good for 10,000 gallons of water so if you have a
pool that holds 20,000 gallons of water then you would need 2 bags for
a regualr shock treatment
Cost of 2 bags of shock: $8

Retail price for sodium hypochlorite to reach 10 ppm free chlorine in
20,000 gallons is less than $3 here. This represents over a pound of
elemental chlorine that will oxidize and gas out a huge amount of
contaminants, including algae.

Shock I feel is the easy way to get rid of alage but it takes the
longest to finally get it clear

The pool will be blue within hours, and clarified in a day or so.