API Test Tube Holder

I kept knocking over the test tubes from my API Master Test Kit when testing the water in my fish tanks so I made this to make them a little more stable.

It holds upto 8 tubes that are MAX 12.75mm OD

It says "fresh" on one side and "marine" on the other to prevent me from confusing the water samples when testing from both tanks of mine at the same time.

The fit is nice and snug, safely holding the tubes even when inverted, but not so snug that you think they'll break.