If you want to dose organic carbon (vodka is just one form) on a small aquarium, a precise graduated burette will surely be required. Precise doses of a couple tenths of an ml. (or less) will be required, at least initially.
Also, you will need to educate yourself. I also suggest that you consider an 'all in one' product like Seachem's Fuel, or Salifert which makes one too (name?).
These products have organic carbon, amino acids, vitamins & trace elements in it. The amino acids, partly become a nitrogen source as well, which is usually required to also control phosphate. I like to dose the amino acids separately as well.
Learning about nitrogen, carbon and phosphorous 'limits and balance' requires some reading & research.
You might begin reading here. This article is a fairly good overview.
http://www.reefaquarium.com/2012/carbon-dosing-in-laymans-terms/">http://www.reefaquarium.com/2012/carbon-dosing-in-laymans-terms/</a>
I also have read extensively elsewhere and research has indicated a slight advantage to using acetate sources of carbon, such as vinegar (acetic acid) or calcium acetate. Many other forms of carbon will work including methanol, ethanol (vodka), sugar(s), soluble polymers, etc.
A lot to get your head around, but it promises incredible results...if done properly.
