Monochloramine, Chlorine, CYA and pH

[waterbear]

No matter what method you choose it will take a lot of chlorine to kill mustard algae. If you do not have a vinyl pool I would not worry about the pH but rather just 'nuke the pool' until the algae is gone.
If you have a pool surface that might be affected by high chlorine levels then I would use either an ammonia based or bromine based 'chlorine enhancer' to take the CYA out of the loop. If CYA levels are high I would definately use bromine or ammonia based products. The algae will die faster but then you have to keep shocking to burn off the ammonia or bromine.