Since you're doing weekly water change, is it possible to get to the alk level you want by just changing salt or mixing salt? For example if you mix red sea blue and black bucket at a ratio of 5:1 you will get approximately 8.6 DKH on your saltwater mix. You can play with the ratio to get to the level you want. I am not suggesting you do this, I am asking the forum if it is possible to do this instead of dosing.