28 Sulphur Nitrate Filter

The sulphur-nitrate filter is an active biofilter that reduces the nitrogen concentration (nitrate) in the aquarium water by denitrification (nitrate reduction).

In contrast to heterotrophic denitrification with a degradable carbon source, the sulphur filter works autotrophically, i.e. the highly specialised bacteria growing on the sulphur fill supply themselves with carbon from the carbonate / hydrogen carbonate / carbon dioxide present in the water. The required energy is taken from the sulphur material (chemotrophic).

The sulphur-nitrate filter must only have a small water inflow (bypass system) so that a low-oxygen environment is created in the filter. Unfortunately, sulphur in spherical form cannot be operated in a fluidised bed process because the sulphur spheres are too soft and the abrasion in the fluidised bed is too high. Redox monitoring is generally not necessary. Automatic flushing is possible and particularly useful for larger systems. 

Video: large filter with automatic flushing system