1-1/2 cups works with my water, sounds like more crushed oyster shell will be needed for you.PoolGuy wrote: ↑Mon Dec 09, 2024 3:08 pm
A few minutes ago in desperation, I added another 1/2 cup or so more lime and a couple three big handfuls of shells. My pH keeps crashing. I am suspecting that my problems may come from not be using enough shells, even though I am following recipe (typically 1-1/2 cups crushed oyster shells for my 15gal batch).
Question: Is there such a thing as too many oyster shells / beach shells / marble?
Calcium carbonate is better at buffering the pH but not much good at correcting a crash.
To answer your question, if the pH is still too low you haven't added too much CC yet.

I'd crush the shell grit finer and double or triple the amount.
What are you using for water?