Stole archipelagourbanfarms's Modular Hydroponic System idea and redesigned so it worked a bit better for me.
Supply hose runs up the center and the top cap is designed to couple with it I used ABS plumber cement on all the threads to prevent it from leaking.
Feb 2021 Update: Added a garden hose threads version of the cap.
The author marked this model as their own original creation. Imported from Thingiverse.