Anerobic methods of removing nitrates are also very risky. I would not risk my fish to the anerobic bacteria extracting the oxygen they need to make glucose from sulfates (SO4) and converting them into sulfides such as hydrogen sufide (H2S) which is also known as rotten egg gas or swamp gas. This stuff is highly toxic (so toxic in fact that its use in undergraduate studies is forbidden). Would not want to be exposing my fish to this stuff. Live plants + waterchanges are cheaper anyways.