"Paul" wrote in message
...
Like how much Limestone. One big piece or smaller ones. Thanks...
"Courageous" wrote in message
...

Exactly. And the limestone keeps the alkalinity from falling.

In fact, the more that the alkalinity falls (i.e., the water is
becoming acidic), the more likely the limestone will react with
the acids in the water to, um, increase alkalinity.

This is why certain fine organic sands are to be preferred in a
marine environment, where higher alkalinity is particularly
important.

C//


I don't know that there is a specific formula as not all limestone is the
same. Limestones vary greatly in their solubility and hardness. I have
about 300-400 lbs of it built up as a waterfall and for structural support
for my biofilter in one end my 1,400-gallon pond (although not all of it is
under water). Nearly all of it is dolomitic limestone (high magnesium
Limestone containing a significant fraction of dolomite), so it is harder
than pure limestone (which has calcite as a primary mineral) and has a
relatively low solubility. Even so, enough of it gets dissolved over time
that it keeps both the pH and the alkalinity in the proper ranges. Oh, and
always clean the rock before use.