Alkalinity

[Delphinus]

Weird.

Are you dosing yet? I'd start by dosing Alk for now to bring that up to targets .. The Hanna's measure in mg/L CaCO3 which convert to dKH or meq/L as follows ..

The instrument directly displays the concentration of alkalinity in ppm of CaCO3. Alkalinity conversion:
1 ppm CaCO3/L = 0.02 meq/L
1 ppm CaCO3/L = 0.056 dkH

There's also this: http://glassbox-design.com/2009/alkalinity-conversion/

.. So I think you want to target your Hanna readings to be in the 150-160ish ballpark. I think..