While I agree that it could be a problem. the tunze osmalator uses an optical eye with a mechanical float as a back up so you don’t have to worry about anything sticking. it also comes with the nice max run time option so in the event that it gets stuck on only a predetermined amount of water can enter the system. I have mine in a 1 gallon top off reservoir. Due to the small surface area of the Biocube and the hood preventing lots of evap I fill my resevoir with 1 gallon once a week. I did my research on nano skimmers and couldn’t find a single one that would fit into the back of a Biocube and skim efficiently at anything but a perfect water level.