I came across this thread where this person did a biological filter media performance test. The result is very interesting. In terms of no3 removal, ehaim substratpro out performed siporax and matrix by a big margin which made me to try it out for no3 removal. Siporax and matrix did do much compare to substratpro.
http://story.raraaqua.co.kr/index.ph...ent_srl=230376