pH module isolation. Ground looping problem.

I have been trying to use arduino with pH probe and ph module in a hydroponic 20 liter tank, both powered with same power supply 220 AC to 5V DC , but i have signal noise in the meassurement, i have read that it could be ground loop problem, i have tried with different RC low pass filter, also tried with external supply like battery to power pH module, but i didn't have good success. In a small cup the signal works perfect.

Any recommendation or tip?

Im using this module.

Thank you in advance.

pH probes can be quite sensitive and challenging. If it works in a cup but not in the tank, it could be due to something in the tank or the way that you have routed the wires. Yes, it could be due to a ground loop but don't ASSUME that that is the issue.

pH electrodes are extremely sensitive to the slightest leakage currents, you probably need better isolation
for the sample and/or measuring equipment. The standard isolation in a power supply isn't nearly good enough.

Thanks for reply. I'm going to try with B0505s 1w 5v A 5v Dc Dc for isolate pH module power.

Any other work around?