A thermometer enables you to observe when the water has obtained a temperature suitable for you to bathe in. The ideal temperature for a hot tub is considered to be 37–38 degrees (Celsius). It is advisable to mix the water a couple of times during heating because the upper water layer is always warmer than the bottom layer. You can order a paddle for mixing the water.
You can choose between two different thermometers. Both are floating on the water so they are very comfortable to use.