"I use this thermometer for my aquarium. It is battery operated with battery included. The probe goes into the water and is connected by a wire to the display unit. Both are mounted with suction cups.
Positive:
More precise temperature readings: .1 degree incriments, either C or F settings.
More accurate than those strips that stick to the aquarium. While the strip read 76 the whole time, the
ESU thermometer readings ranged between 73.4 and 77.3
Its stays in place, doesn't get knocked around and thus become temporarily unreadable like the ones that sink to the bottom.
Negative:
One more ugly wire & object inside the aquarium (though its not that bad).
Sometimes the unit doesn't come on or the screen goes blank. I haven't been able to figure out why though I've always been able to get a reading out of it if I jiggle it a bit.
Batteries will eventually need replacing.
Overall, I prefer this type of thermometer to the other choices."