There have been many discussions in fish forums on adopting anaerobic denitrification in deep sand as used in saltwater, but it has not gotten traction in freshwater. Saltwater has more diverse fauna in live sand to carry out denitrification at higher efficiency than in freshwater. Making artificial saltwater is expensive and tedious, so saltwater folks employ every biochemical filtration option available to minimize WC. Freshwater is cheap and nitrate reduction can be achieved much easier by water change or growing plants. Anaerobic denitrification in freshwater is too slow and hazardous (due to potential release of toxic gases) to worth the effort.
Chloroplasts of all green plants and algae are symbiotic descendents of cynobacteria. It's good to know that there is a diversity of other photosynthetic bacteria besides cyanobacteria that utilize different processes to capture sunlight energy to make food.