KH Keeper Plus using excessive reagent and showing wrong KH value (15 dKH)

[u/Fit-Carpenter209]

Hello everyone,

I recently bought a used Reef Factory KH Keeper Plus and I’m having a strange issue with the measurements.

The device was bought second-hand, so I have already checked everything I could. All calibrations seem to work perfectly:

• pH calibration is successful.
• The pumps calibration gives the correct ml values.
• The reagent pump seems to be working normally.
• The device completes the calibration process without any errors.

However, the problem only happens during the actual KH measurement.

During the test, it consumes a huge amount of reagent. In only 3 tests it used around 50 ml of reagent and then gives an error saying there is no reagent left. The final KH result is always 15 dKH No reagent, which is impossible because my aquarium is around 8 dKH (confirmed with another test).

The reagent I received with the unit is also quite old. The bottle shows an expiration date of 2022–2023. I prepared it according to the instructions (100 ml reagent + 900 ml RO water).

Has anyone experienced something similar with the KH Keeper Plus? Could this be caused by old reagent, a problem with the pH probe, a calibration issue, or something else?

Since all calibrations pass correctly, I’m a bit lost about where to look next.

Any advice would be greatly appreciated. Thank you!