Goose, it's not going to help you. IME LPS and softies do a bit better when there is some detectable nitrate. JME
Andy,
My tank is a 65g with a 20g sump. No idea of actual water volume after rock, sand, etc.
For sugar I started with a 1/4 of a teaspoon. I did that every other day for three doses, saw no change. I increased to a half of a teaspoon, every other day for three doses, saw very little change, (I was using an API at the time so hard to say), then went up to a full teaspoon, nitrates dropped from 40-50ish to 0 before the sencond dose so within 48 hours. I continues to dose the full teaspoon once a week inbetween water changes. I stopped using sugar for the time being. Either my nutrient problem was something internal from the tank, or my bacteria caught up but I do run with zero nitrate now. I still test for it weekly. If some showed up I wouldn't hesitate to use sugar again.
For vodka I was using started with 1mL and worked my way up to 5mL.
I haven't noticed any signs of overdosing myself like the white bacteria bloom. I know that using carbon sources can drop 02 levels but betweenthe surface aggitation, the protein skimmer, and the macro algaes, I never saw a problem myself.
HTH