Circuit, pcb design in the video.
Arduino code on the smd attiny45/85.
PCB size: 20x25mm / ~0.8×1 inch
Powered from 5V USB mini.
This small device check the water level every ~12 hour. If the water level low, the small water pump turn on until the water level reach the sensors.
The sensors not on power between the level checks, so no electrolyzis.
How to program attiny with arduino: