fishless cycling - pH problem?

Thusly "muddyfox" Spake Unto All:

I'm trying to cycle my new aquarium using Ammonia. Things seem to be
on track except that the pH is climbing to very high levels (pH 8.4
today) and I'm concerned that the bacteria I need for my nitrogen cycle
will not do well in these conditions.

Ammonia has a pH of about 10-11 so it's not all that surprising that
adding pure ammonia causes pH to rise.
pH 8.3 is also the equilibrium point for hard water, so if your water
has high KH that's the pH you're going to have when the CO2 in the
water is in equilibrium with the CO2 of the atmosphere.

That said, a pH of 8.4 wont inconvenience your de/nitrifying bacteria
in the slightest. You don't want the pH to go over 9.5, though.

I see others have suggested the rising pH may be due to
limestone-containing sediment in your tank, but that'll not be the
case - one can't raise the pH of a tank to 8.3 with limestone. I wish
one could, but the equilibrium point will be in the region of 7.5-7.7,
because the limestone dissolves so slowly.

Also, like others have noted, your tank is already cycled, as ammonia
& nitrite is zero, and nitrate is 30 ppm.

On a sidenote, using pure ammonia isn't really necessary, one can also
simply feed the tank sparingly (without any fish being in it). The
food will rot & provide ammonium for the de/nitrifying bacteria. I
don't know why so many seem to prefer to use ammonia; possibly it
seems cleaner & more controlled.