Freshwater home aquarium biofilter microbiome
New freshwater home aquarium systems have higher risk of ammonia and nitrite accumulation leading to toxicity and fish death. A major source of variation in home aquarium systems is fish load, although there are no known peer-reviewed studies demonstrating how differences in fish load may affect ammonia and nitrite loading, and subsequently influence microbial community and nitrifier succession within aquarium biofilters. Fourteen new home aquarium systems were established and stocked with a range of fish loads and maintained for six months, during which aquarium water and biofilters were sampled to monitor ammonia and nitrite concentrations and microbial community succession. As expected, increasing the number of fish in an aquarium significantly increased the maximum ammonia and nitrite concentrations, although ammonia and nitrite were eventually depleted within similar timeframes. The comammox Nitrospira were among the most abundant nitrifiers and present in all biofilter samples regardless of fish load, whereas ammonia oxidizing bacteria were at relative low abundance although increased in abundance in aquaria with higher fish loads. Ammonia oxidizing archaea (AOA) were absent from all biofilters, contrasting with previous reports of AOA abundance in biofilters, suggesting their introduction to aquaria is more stochastic compared to other nitrifying microorganisms. Aquaria with higher fish loads contained microbially communities compositionally different from those with lower fish loads, dominated mostly by Pseudomonas, Rhodobacter, and Planctomycetes, suggesting that lower fish loads do not provide sufficient organic carbon and nutrients for extensive biofilm formation, or that they require considerably more time for biofilm maturation and specialization.
New freshwater home aquarium systems have higher risk of ammonia and nitrite accumulation leading to toxicity and fish death. A major source of variation in home aquarium systems is fish load, although there are no known peer-reviewed studies demonstrating how differences in fish load may affect ammonia and nitrite loading, and subsequently influence microbial community and nitrifier succession within aquarium biofilters. Fourteen new home aquarium systems were established and stocked with a range of fish loads and maintained for six months, during which aquarium water and biofilters were sampled to monitor ammonia and nitrite concentrations and microbial community succession. As expected, increasing the number of fish in an aquarium significantly increased the maximum ammonia and nitrite concentrations, although ammonia and nitrite were eventually depleted within similar timeframes. The comammox Nitrospira were among the most abundant nitrifiers and present in all biofilter samples regardless of fish load, whereas ammonia oxidizing bacteria were at relative low abundance although increased in abundance in aquaria with higher fish loads. Ammonia oxidizing archaea (AOA) were absent from all biofilters, contrasting with previous reports of AOA abundance in biofilters, suggesting their introduction to aquaria is more stochastic compared to other nitrifying microorganisms. Aquaria with higher fish loads contained microbially communities compositionally different from those with lower fish loads, dominated mostly by Pseudomonas, Rhodobacter, and Planctomycetes, suggesting that lower fish loads do not provide sufficient organic carbon and nutrients for extensive biofilm formation, or that they require considerably more time for biofilm maturation and specialization.