Ok let me make sure I'm understanding correctly.
By channels in your styrofoam, I'm assuming you mean a cut or slot on the top so it fits.
The tank sits on the styrofoam which would mean the probe is making contact with the bottom or underside of the uth.
Also, with the tank on the styrofoam, is the styrofoam just big enough for the probe or is it on the whole bottom of the tank. I'm assuming the former for ventilation purposes. I'm also using a tub of that makes a difference.
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