DFRobot probes

Does anyone have any experience with the DFRobot pH and conductivity probes? I'm working on a project for my work placement in which I'm building an IoT system to get data from an anaerobic digester bin (basically a big compost heap which produces compost, biogas and water), and I'm concerned they won't hold up submerged indefinitely in less than ideal conditions.

I've seen the probes that atlas scientific have but my supervisor is hoping for something with a smaller price tag. (I'm in Australia, the pH kit is like $500...)