How much oyster shell?

I added two bags of oyster shell to the "bucket" at the top of my
falls. Used about 15 lbs. Waited a few days and took a reading and my
PH was really high. Off the charts on my test strips. I thought it
would level out around 8-8.4 or so but it was way up there. Couldnt
figure that out. KH and GH havent seemed to raise any at all. But, my
falls evaporate water out of the pond so fast that I have to top up
every two days or so with VERY acidic water with VERY low KH. I havent
put any fish in this pond yet out of fear that the water just wont
stabilize. It is a new pond. I never get any NitrIte nor NitrAte
readings, even though my tap water has a little NitrAte, I have been
adding bacteria but Im just not sure I want to risk putting the fish
in. Especially not my new Platinum Ogon.