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

this is a simple adapter ring for a 40mm test tube, so you can suction cup it to the wall of an aquarium.

why might you ask, do you need this ring or a 40mm test tube in an aquarium?

Well, if you need temporary Co2 and you want to diffuse it a 100% you can pump it into an upside down container and it will diffuse over time. I am using this setup to grow plants until my fish arrive and perhaps intermittently as needed.

requires:
1x m3 nut
1x m3 x 16mm bolt
suction cup


I now have