Pentair Aquatics' Big Temp-Alert constantly reads out water and air temperatures (the Little Time or Temp only does one at a time). This is a large-face digital thermometer measuring 4" X 4" X .75". It displays both the aquarium water temperature and room temperature in Fahrenheit. The all plastic probe has a 3 foot cord. The alarm will sound and LED will flash in the following settings: High Temp Alert Only (probe), Low Temp Alert Only (probe), Both High and Low Temp Alert (air/room), Both High and Low Temp Alert (probe).