Alkalinity

[Reef.]

My salt alk is 7kh, I tested a fresh mix and it’s correct but my tank is around 6.4kh, I’ve no coral yet, just wondering what else in the tank could lower the KH part from coral? I’ve a cleaner shrimp but thinking that would t do it?

My ph is 8.15
Salinity is 35

I used salifert test kit (planning on moving to Hanna for alk)

 

[lapin]

Nitrifiers use alkalinity as a carbon source. Part of the cycle.