I purchased a set of 1 inch diameter glass tubes for propagating plants that came with a wooden base, and I wasn't thrilled with the base.  I designed this model to:

• Print without support
• Use minimal material
• Block as little of the tube as possible
• Be very stable
• Allow multiple prints to be linkable in a line

This model fits all those criteria nicely.  If you want to permanently connect them together, there's a small hole in the connector that fits a short length of filament; melt and flatten the ends into the countersunk holes to make a permanent chain if desired (but they're quite stable even without that).

I had some trouble printing with PETG (I think the thin bits are too flexible/soft while in the warm chamber), but PLA worked nicely.

Designed in TinkerCAD - https://www.tinkercad.com/things/gmC1MtN5tmA-propagation-tube-holder-for-1-tube