Elaine T wrote:

JGW wrote:
I've been adding a lot of baking soda as a buffer. I've been checking
the salt level in my pond, and it doesn't show any change. I don't
want to kill my plants.

Does anybody know whether most salt test kits test for sodium,
chloride, or both? Is it the sodium in salt that kills plants?

Any reason I can't use powdered magnesium/calcium carbonate to
increase alkalinity as long as my general hardness is also low?

I'm not an experienced ponder, but wouldn't seashells or crushed coral
work to add hardness and alkalinity? Plants require some Ca++ and Mg++
anyway.

You're right - I think JGW's concerned about the possibility of raising
general hardness too much. If it's low to begin with, I wouldn't worry.
--
derek