[Delphinus]

A sulfur based denitrator uses aragonite media to buffer the output as it will be low in pH, so it conditions the effluent before being returned to the tank. Any sulfur based reactor has both sulfur media and calcium media, either mixed together as in the case of Caribsea "No-NO3" media, or in separate layers using Caribsea LSM (or other pure elemental sulfur granules) in one layer and a calcium reactor media in the other.

What Psyire (and I) have done with our reactors is use a 2 stage calcium reactor design and use exclusively sulfur in the first stage and exclusively aragonite in the second. Typically a 2 stage reactor uses recirculation on the first stage and single-pass on the second, which I think in the case of an anaerobic bacteria colony would only help with the overall efficacy of the reactor.

A calcium reactor does not consume O2 but uses CO2 to lower the pH to dissolve the aragonite media.

Psyire, what sort of nitrate levels are you running? While I'm excited that you're trying this, on the other hand that's not a heavy bioload for a 180g by any means.. I'm sort of surprised you would be having nitrate accumulation problems ... (bluntly put, you shouldn't be).