Grow Mediums What is everyone using to control and measure water temps?

[NorthernLights_420]

I use the blue lab combo meter ec/ppm, PH, temp. I calibrate it once a month so it remains very accurate. My probes are in the res full time. It is easy to check the status with just a touch of a button.

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Same meter I have. I use basement cement floor to keep temps in check. Hydroguard in case temps get warmer