KH levels fluctuate

[Rlumenator]

My DK goes up to 11-12, then over a matter of days, it drops to 9. I have added Seachem "Reef Builder" which raised carbonates, but it doesn't seem to stabilize. Does adding Magnesium help stabilize the hardness? Thank you.

 

[ChrisRD]

Your tank will consume Alk on a continual basis, so you have to keep supplementing it.

It's important to keep Ca and Alk in balance, so IMO it's best to supplement with a 2-part additive like B-Ionic or use kalkwasser for topoff of evaporation (or use both methods together).

Depending on what you keep in your tank and how large it is, your Ca and Alk demands could get very high in which case many people start using kalk reactors and Ca reactors to help automate the task of keeping these levels up.