You can lower your ALK
by using Muriatic Acid. Dosing slowly, as in, dosing in MLS, as this will lower your PH also, but the PH will bounce back. But as CB explained, your ALK
will come down on its own in a bit of time, as SW
tanks use this up. 12dKH is not a bad number, its the top of wehre it should be, but not over by any means.