Thingiverse
I really like the design by lanepulcini, and have used their design for quite some time. I recently have started testing GH (General Hardness) and KH (Carbonate Hardness) in my Shrimp Tank and I needed a bigger test tube holder. So building upon the original design, I incorperated extra tube holders to test everything together. Will post pictures once printed.
Direct link to the original creator's page
Printables
Thingiverse
Printables
Thingiverse
Thingiverse
Thingiverse
Thingiverse
Printables
Click the "View on Thingiverse" button above to visit the original model page on Thingiverse. You can download the STL file directly from the creator's page for free.
This model is compatible with most FDM 3D printers (Creality Ender 3, Prusa MK3S+, Bambu Lab, etc.) and resin printers (Elegoo, Anycubic). Check the original page for recommended print settings and materials.
Yes, this model is available as a free download on Thingiverse. Some creators accept tips or donations.
Check the license (see original page) on the original Thingiverse page. Most STL files can be modified using free software like Blender, TinkerCAD, or Meshmixer.