My earlier posts have been about the dark green algea all over the plaster of my NEW pool. After doing a test in the hot tub only...muriatic acid made it go away. Chlorine has not worked (old theads will give more detail), but no, it is not a metal stain... so

A few questions:

1. What is the maximum concentration of mutriatic acid that can be safely used in a plaster pool? (14400 gal)

2. Can the PH be lowered a significant amount for a period of time then raised to normal levels without potential damage to the plaster?

3. Should the DE in the filter be changed or backwashed to eliminate any residual algea?

4. As an aside, to eliminate the possibility of metal staining, will muriatic acid also remove Cu or other metals from the surface of the pool?