On 21 Apr 2006 20:28:43 -0700, "robv60" wrote:

Checked the water this morning and the PH
was 7.2 and the KH was around 80. It was 8.4 and 120, respectively. So,
Im hoping to add the oyster shell to have something in the pond that
will disolve as needed to help me keep up with the shifting water
quality. Just need to know how much I should add.

Five pounds is probably a good number, but KH is surprising when you
use ground limestone, never tried oyster shell. You may be
disappointed to see your readings don't change quickly because of the
oyster shell. To begin with the calcium in limestone doesn't
dissolve into the water until the pH allows, (below pH 7.8 I think.)
I've had readings of 1 degree KH (17.8 ppm.) immediately after a rain,
but pH still reads over 7, sometimes as high as 8 but never a crash.
I add a cup of ground garden limestone when it seems to disappear from
the bottom of my 1500 gal pond. (It doesn't dissolve quickly like
baking soda.) The quantity of limestone is pretty much a guess, I
just keep enough showing I don't run out. (I used to keep it in a
sock, panty hose, in the filter flow, but I became afraid I didn't
check it often enough.) Baking soda is very temporary for me and it
also keeps my pH so high the limestone doesn't dissolve, so I hold my
breath and use ground limestone instead, even though it reads low, it
seems to work well.

I also add a 1" x 5" diameter chunk of plaster of paris to bring up
the GH occasionally, but the fish don't seem to care one way or anther
about that, or the limestone. It is just that my KH and GH readings
stay so far below what is recommended by "Experts", so I do it
occasionally to try to improve the toilet bowl existence for the fish,
but I have no indicators that the GH wouldn't be just as well left
alone.

Regards,

Hal