I designed this bracket to hold a water level sensor, a light sensor and a temperature sensor on the side of a fish tank.

The part for the water level is adjustable. It's part of an arduino project to monitor a recifal tank: https://github.com/reivaxy/aquaMonitor

UPDATE: New design "aquaMonitor10mm.stl": taking advantage of the transparency of PETG (might also work with transparent PLA), the light sensor is now protected against water projections, since the case is closed around it. I've had to replace two sensors because after more than one year they get oxydated because of micro drops of salted water they were getting. The new design will preserve the sensor agains these projections.

I can generate stls for other glass thickness, if you ask, the aquaMonitor10mm.stl file should work for 10-12mm thick glass.

AquaMonitor6mm.stl is the old design, for 6mm thick glass.