Round plug for hydroponics

This is a simple flat lid for my hydroponics set. When using less plants than the maximum, light was leaking into the water which created mold. These simple flat lids blocks the light from entering the hydroponics set. 

Link to set https://www.aliexpress.us/item/3256806547258727.html

PS: the lid (cap) can be used for anything else.

Design by Mika255 on MakerWorld (license: CC0).