dosing help

[makana]

well right now I am testing the tank levels daily and dosing when it gets too low. I am still trying to figure out a dosing level that will maintain my alk. As for water changes I do a 10% weekly. What I have been doing for a couple weeks is dosing my water change water higher than the levels I want to bring the tank back to the levels I want.

What I can't understand is were my alk is going. It dropped 1dkh a day with nothing added to the tank. I can't see coraline using that much and nothing else in there should be using much at all.