Every pond should have a thermometer in the pond or skimmer to determine when to add bacteria, fish food and when to do other maintenance chores.
Water temperature determines when to shut off the bottom drain, when to shut of the filtration pumps and when to add a pond winterization kit.
Nycon Thermometers have clear plastic casing and easy to read Celsius and Fahrenheit scales.
T-1 Submerged Thermometer
T-2 Floating Thermometer