Probes will generally accumulate some amount of biofouling over time. Cleaning them periodically ensures they’ll keep recording good data! A nylon grout brush or even a cotton swab can be a good tool to clean the probes.

For the conductivity probe, make certain to clean inside of the small gap at the bottom of the probe

For pH, carefully clean around the glass bulb at the end of the probe.

For dissolved oxygen, use a soft microfiber cloth or tissue to carefully clean off the plastic membrane at the end of the probe. If the membrane tears, the probe will unfortunately no longer provide accurate readings.