40mm O.D. Test tube to suction cup adapter

thingiverse

This is an easy adapter ring for a 40mm test tube, allowing you to secure it firmly to the wall of your aquarium using a suction cup. You might wonder why you need this ring or a 40mm test tube in an aquarium. Well, if you require temporary CO2 and want to diffuse it at a 100% rate, simply pump it into an upside-down container and let it diffuse over time. I'm utilizing this setup to cultivate plants until my fish arrive and possibly intermittently as needed. To assemble the adapter ring, you'll need: 1x M3 nut 1x M3 x 16mm bolt Suction cup I've since created a dual version of this design, which can be found here: https://www.thingiverse.com/thing:3551829