"The Vodka method is characterized by the controlled dosage of a carbon source (vodka or other) to stimulate the growth of bacteria to assimilate Nitrogen and Phosphate. The nutrient and bacteria are exported via protein skimming. Skimmer production can be extremely high and any mechanical media will clog more rapidly due to bio-film production"
"The addition of vodka/ethanol is thought to increase bacterial biomass. For this, vodka addition would result in bacterial growth and reproduction. During this process nutrients in the water (including NO3 and PO4) are taken up for the formation of new macromolecules that are needed in cell synthesis and viability. Due to this rapid growth and reproduction, NO3 and PO4 can drop quickly from detectable levels by most test kits on the market. The increased biomass of the bacteria leads to a notable increase in skimmate production, removing more waste than without vodka addition. The increased skimmate is thought to remove the bacteria or bacterial biproducts that have assimilated the NO3 and PO4 within the water column leading to NO3 and PO4 depletion."
All the above is based on the
Redfield ratio wikipedia:
Redfield ratio or Redfield stoichiometry is the molecular ratio of carbon, nitrogen and phosphorus in phytoplankton. The stoichiometric ratio is C:N = 106:16:1. Redfield described the remarkable congruence between the chemistry of the deep ocean and the chemistry of living things in the surface ocean.
Here is my understanding, if the N and/or P is high in the tank; it will need lots of carbon source so that the bacteria can process them to maintain the Ratio.
Carbon sources are ethanol or grain alcohol aka Vodka or Everclear. Other carbon sources are sugar (glucose,sucrose,..) and vinegar (acetate).
Vodka dosing will increase the carbon source in the tank. To maintain that ratio, bacteria will consume N & P that the skimmer will remove. Thus, you
must have a skimmer to remove the bacteria with Vodka, sugar or vinegar dosing. Carbon dosing a tank requires a working skimmer to remove the N & P.
Once the excess N & P are removed i.e, PO4 & No3 reading is zero, you can maintain a minimum carbon dosage to keep N & P in check.
As for dosage, it will depend on the tank's C:N
. Experiment based on the recommended dosage from RK link.