Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
I used a Sharpie marker (fine tip) and wrote on each bottle the number of drops.
Also, on the back of each card are the instructions. I made a little stand that holds several bottles, the cards and the test tubes, all organized. The card is in a slot that stands it up for mixing, then I just turn it around to see the colors.