It really depends on your bioload. You should be testing for Nitrates since you started. Once those drop off you should know your daily dosing level. Are you adding any new livestock? That could affect how much you dose as well. Don't go on autopilot while dosing vodka it can have some bad consequences.
On my 115g + 40 gallon sump, I was only dosing 5 ml and had 0 nitrates and phosphates.