For those of you who test in a different room than where your tanks are:
1. Cut a piece of soft, knot free pine 2X4, 8 inches long. You can even sand it up if you want to make it really smooth.
2. Drill 7 holes in a row accross it. Use a 9/16 or 5/8" drill bit. Drill holes straight down and about 1/2" deep.
3. Take marker pen and mark each hole for each test.
pH, Ammo, NO2
Now you have a handy way to hold all your tubes as you grab samples, carry to test area, and keep which test is which.
Extra tip - get a dosing eye dropper at drug store with ml/tsp marks on it for easy, precise filling of the tubes.