Just want to remind everybody about these.
As you can see they are really cheap!
And---- are very accurate.

We suggest they are NOT left on suction cup...and NOT hung on the interior glass wall.
Instead remove the suction cup and stick them right in to the soil. Or, simply lay it flat.

Easy to move around and monitor different areas of an enclosure and cheap enough to have more than one /enclosure

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QT tanks

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the tip is stuck into the substrate
( D tinctorius "New River" )

They work great for floating in tadpole water as well.

I recently found 3 of these on a sale table for 99 cents each !!!

Floating Thermometer - Economy | That Fish Place