The crushed corals tend to increase the KH gradually instead of instantly hence why they are much easier to use than most chemicals and tablet supplements that contain calcium carbonate which increases both the pH and KH.
High nitrate can make your water acidic as it "eats" up the buffering properties of your tank water. This may be why you saw your pH elevating a bit due to slight improvement of water conditions after the gravel serving as nitrate trap has been removed from your tank.
High nitrate can make your water acidic as it "eats" up the buffering properties of your tank water. This may be why you saw your pH elevating a bit due to slight improvement of water conditions after the gravel serving as nitrate trap has been removed from your tank.