This Makes Aquaculture Disinfection Less Effective — Here’s Why

How effective is peracetic acid at actually killing bacteria in recirculating aquaculture systems? In this video, I break down a 2024 study published in Aquaculture by Sanni L. Aalto, Lone Madsen, and Lars-Flemming Pedersen: “Peracetic acid mode-of-action on aquaculture microbes evaluated by dual-staining flow cytometry.” The researchers used dual-staining flow cytometry to track live and dead microbial cells after exposure to different concentrations of peracetic acid (PAA). They tested both the fish pathogen Aeromonas salmonicida and microbial communities from RAS water. One of the most interesting findings was that dose alone wasn't the whole story. At 10 mg/L PAA, 95% mortality of A. salmonicida was reached in about 14 minutes. At 2 mg/L, it took approximately 59 minutes, while 1 mg/L required much longer. Adding dissolved organic matter reduced PAA effectiveness even further. And this becomes particularly important in real RAS water. As organic matter increased, PAA disinfection efficiency decreased. The study suggests that organic matter accelerates PAA decay and can also contribute to microbial aggregation, potentially protecting bacteria from the disinfectant. In this video, we explore: How peracetic acid kills aquaculture microbes Why PAA concentration and exposure time both matter What happens to Aeromonas salmonicida Why organic matter can interfere with disinfection How flow cytometry can distinguish living and dead microbial cells What these findings mean for microbial management in RAS The study also highlights an important practical trade-off: concentrations high enough to achieve strong rapid disinfection may exceed concentrations considered safe for fish or interfere with biofilter performance, meaning that simply “adding more disinfectant” is not necessarily a viable long-term strategy. Paper: Aalto, S.L., Madsen, L. & Pedersen, L.-F. (2024). Peracetic acid mode-of-action on aquaculture microbes evaluated by dual-staining flow cytometry. Aquaculture, 578, 740129. #Aquaculture #RAS #Microbiology #FishHealth #PeraceticAcid #FlowCytometry #AquacultureResearch #FishFarming #ScienceExplained For the thumbnail, I would use something much shorter than the title: “WHY DIDN’T THE BACTERIA DIE?” with a RAS tank + bacteria + PAA visual. That gives you a stronger curiosity gap than putting the paper title on the thumbnail.