This is a hydroponics remix of O3D's self-watering planter.
It fits this sort of 7cm white-label water level indicators with an outer diameter of 14mm:
https://www.dehner.de/produkte/wasserstandsanzeiger-M200006794/
You should be able to find similar ones at every other garden market.
Don't save on infill for the reservoir, otherwise it might leak.
Have fun!
HydroPlanter_v4.stl | 1.4MB | |
HydroReservoir_v4.stl | 106.5KB |