Alkalinity stability?

[Reef.]

I’m trying to get my tank ready for corals, I use TMPRo salt, so aiming for KH at 7-7.5, atm my alk is 6.6, I’ve added baking soda to bring it up to 7.0, works great but the next day it has dropped again to the same lvl, never seems to drop past 6.6kh, as said no corals and no coralline algae, not sure what is using the alk.
I plan on dosing All For Reef when I get corals but in the meantime what’s the best way to get my alk stable? or do I just need it stable the day before the corals arrive by adding baking soda, bringing the alk to 7kh then adding the coral and then start dosing the AFR? Or should I keep dosing baking soda daily now, or just start with the AFR even tho I have no corals yet?

 

[Jekyl]

I just add baking soda to my top off water

 

[mdb_talon]

I cant answer why it keeps going down, but I would say try to get it to where you want it before adding coral. Jumping from 6.6 to 7 after you add coral is not a big deal just think it would be good to work out what you need to do to stabilize it before adding the coral. Then of course as the coral grows you may need to increase dosage, but at least you got a good starting point.