Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
There are very small boxes of baking soda, and it is pretty cheap.
You might be able to cut that recipe in half, but I would not trust the measurements for a smaller batch than that.
If you belong to a planted tank club why not do this once at a group meeting, and share out the results, then each time you meet a different person brings enough to share with all of you.