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How PNS Bacteria Promote a Healthier Aquarium

In the aquarium hobby, there are Good Tanks and there are Bad Tanks. Good Tanks are stable, do not experience abrupt fluxes in water quality and do not foster pests or disease. Bad Tanks constantly require the addition of chemicals or new filtration in order to maintain water quality. Because of this, they often cultivate unseemly pest algae and opportunistic pathogenic bacteria. Nature tells us that the primary difference between the two is a matter of ​functional microbial diversity​. “Beneficial” microbes directly consume both dissolved and solid wastes, produce valuable nutritious compounds and ward-off destabilizing pests/disease.


Coral reefs are some of the most diverse and productive ecosystems on the planet because of the incalculable microbial diversity they contain. Therefore, functional microbial diversity is one of the most important considerations to establishing a successful reef aquarium.


A Brief Note on Microbes in the Aquarium

No reef aquarium is successfully maintained without establishing a stable and functional microbial community. It is well known that nitrifying bacteria species (​Nitrosomonas,​ ​Nitrobacter​, etc.) are paramount to detoxifying ammonia/nitrite. The value of these nitrifying “biofilter” species is so well-recognized that it has led to a menagerie of commercial probiotics. These products allow the aquarium keeper to ensure that their tank is seeded with specific bacterial strains. Once these bacteria establish a successful population, they sustain themselves by consuming biological wastes--thus generating greater stability for the reef’s other inhabitants.

Microbial seeding through efficacious probiotic products is one of the most important tools available to the 21st Century Reef Aquarist. By promoting the establishment of more and more beneficial bacterial populations, the aquarist is promoting a greater overall functional microbial community. Though there are still relatively few commercial strains of aquarium bacteria available, some new emergents, such as ​Rhodopseudomonas palustris,​ offer considerable benefits to the reef aquarium.


R. palustris​ is a gram-negative, purple non-sulfur bacterium belonging to the family Bradyrhizobiaceae. Using its metabolic superpowers, wild ​R. palustris​ colonies stabilize and enrich marine and freshwater ecosystems worldwide. It has been long studied for its applications in wastewater management and commercial aquaculture. This is because​ R. palustris​ is an aggressive consumer of nitrogenous wastes, but more importantly can consume them in a variety of ways and convert them into nutritious compounds.

Limitations of the Conventional Biofilter

The conventional nitrifying biofilter species, ​Nitrosomonas,​ can only primarily utilize ammonia as an energy source. Using oxygen, ​Nitrosomonas oxidizes ammonia into nitrite, which is then oxidized into nitrate by a separate biofilter species such as ​Nitrobacter​ or ​Nitrospira. Interdependent synergy bet