How to lower nitrate?

The way to reduce nitrate is to use a Carbon source.

Known carbon sources include Vodka, vinegar, sugar, citric acid, honey, dextrose, but also bio-pellets is a carbon source

In DSR we opted for the approach with vinegar, later i extended it with a mix of sugar (the Carbon V/S mix). We also have a customised dosing table for this Carbon V/S mix.

The condition to be able to reduce nitrate using a carbon source, is that there must be some Phosphate present. Preferably to be kept at level 0,03-0,08ppm. It sounds very contradictory, but at lower levels (0,0<0,02ppm) dosing Phosphate will help to reduce nitrate to lower levels. 

The dosing of a Carbon source, especially vinegar/sugar can encourage the growth of sponges. Therefore dose nitrate to stabilize nitrate at a desired level.

When dosing carbon watch out for stress signals: milky water,  fish breathing heavily, slime on the corals, rocks and windows.  Half the dose in steps when this happens