I used that versa pump you have for a year or two on my Ca reactor and had good luck with it. Ecotech advertises it as continuous duty and suited for a reactor. The tubes need to be replaced frequently. Have to calibrated it lately? If unsure about how accurately it’s dosing, you can periodically check the flow rate with a graduated cylinder. Mine was always spot on unless the tube was worn but they last for a few months at least at a moderate dosing rate. I agree the kamoer is a more heavy duty pump but this may not be your issue. Like Brian said, how are you regulating pH?