Application of nitrifying supplements to aquarium biofilters
The home aquarium industry is comprised of an estimated 9 to 12 million home systems in North America alone, containing hundreds of millions of individual aquatic organisms and generating a global annual revenue of $70-billion CAD. Many home aquarists minimize ammonia and nitrite accumulation in newly established aquaria by using conventional nitrifying supplements (CS), which augment filter-associated nitrifiers. These supplements contain nitrifying populations, but research on their microbial community composition and in situ effectiveness is lacking. Here we tested enrichment cultures containing comammox Nitrospira (CX) and the ammonia-oxidizing archaeon Ca. Nitrosotenuis aquarius (AQ) for use as nitrifying supplements for newly established aquaria, evaluating their efficacy alongside a representative CS culture. The results demonstrate that inoculating new aquaria with nitrifying supplements resulted in unique nitrifier profiles within each treated group of aquarium biofilters and that these nitrifier populations differentially modified overall ammonia- and nitrite-oxidizing activity. Maximizing supplement dosage was important for ensuring effective oxidation of ammonia to nitrate. Treating aquaria with CX, either as the sole supplement or in combination with AQ or CS, mitigated ammonia and nitrite accumulation and maintained ammonia and nitrite at low concentrations when aquaria were treated with the highest dose. Whereas 16S rRNA gene sequences associated with CS were detected rarely within biofilter profiles, those associated with CX and AQ established early and persisted temporally. Overall, these results demonstrate how nitrifying guild members might be differentially adapted to home aquarium condition and highlight strongest potential benefits when using CX as a home aquarium nitrifying supplement.
The home aquarium industry is comprised of an estimated 9 to 12 million home systems in North America alone, containing hundreds of millions of individual aquatic organisms and generating a global annual revenue of $70-billion CAD. Many home aquarists minimize ammonia and nitrite accumulation in newly established aquaria by using conventional nitrifying supplements (CS), which augment filter-associated nitrifiers. These supplements contain nitrifying populations, but research on their microbial community composition and in situ effectiveness is lacking. Here we tested enrichment cultures containing comammox Nitrospira (CX) and the ammonia-oxidizing archaeon Ca. Nitrosotenuis aquarius (AQ) for use as nitrifying supplements for newly established aquaria, evaluating their efficacy alongside a representative CS culture. The results demonstrate that inoculating new aquaria with nitrifying supplements resulted in unique nitrifier profiles within each treated group of aquarium biofilters and that these nitrifier populations differentially modified overall ammonia- and nitrite-oxidizing activity. Maximizing supplement dosage was important for ensuring effective oxidation of ammonia to nitrate. Treating aquaria with CX, either as the sole supplement or in combination with AQ or CS, mitigated ammonia and nitrite accumulation and maintained ammonia and nitrite at low concentrations when aquaria were treated with the highest dose. Whereas 16S rRNA gene sequences associated with CS were detected rarely within biofilter profiles, those associated with CX and AQ established early and persisted temporally. Overall, these results demonstrate how nitrifying guild members might be differentially adapted to home aquarium condition and highlight strongest potential benefits when using CX as a home aquarium nitrifying supplement.