The reason for keeping the entire device under water is to avoid any temperature difference between the device and the tank water. If there is a difference some distillation will occur - water will migrate from the warmer to the cooler area, which changes the KH of the tester water.
Are you sure there is no leakage between the pvc tube and the bottle neck? If so, that has to be the easiest one yet to make. (But not the most unobtrusive or most elegant or coolest!) |