Yes the ones I use are the smaller ones that are kept inside the cage. They are fairly inexpensive. The ones kept outside the cage with the sensor inside it work quite well. But for something simple to keep in a tub in a rack, those are a waste of money IMO. The more expensive ones are probably better, but not economical when you have upwards of 30+ tubs. I'm still searching for an economical solution and open to suggestions
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