I used Vodka very successfully for at least 7-8 months, however there are drawbacks, one of them was catastrophic.
I noticed that my tank became increasingly riddled with brown powdery algae on the glass and was constantly cleaning it away.
The skimmer, as expected, pulled more from the water column, and what it did pull was black and horrible. Instead of a weekly skimmer clean, it was cleaning the cup out every 3-4 days.
Cyanobacteria began to rear it’s ugly head, however because my tank is coral dense it could not get a purchase.
I knew that I had to closely monitor my nutrients and checked on both phosphate and nitrate far more regularly than I had done before (every three days), ensuring that they did not bottom out.
Unfortunately, this was not good enough.
Within a three day period the Vodka dosing consumed all nutrients, and I can only assume they hit zero. When I tested phosphate and nitrate they were 0.003ppm and 0.2ppm respectively, but I could see something was drastically wrong!