Effects of formaldehyde on nitrification in biofilters of small‐scale recirculating systems

Aquaculture Research
By: , and 



Florfenicol (Aquaflor®) is the only U.S. Food and Drug Administration (FDA) approved drug for treating diseased fish reared in recirculating aquaculture systems (RAS). Treating diseased fish in RAS is challenging because of the potential to damage nitrifying bacteria in the biofilters. Impaired nitrification can lead to concentrations of ammonia and nitrite that compromise fish welfare. The objective of this study was to determine the effects of a FDA‐approved parasiticide and fungicide, Parasite‐S® (formalin), on biofilter nitrification. Stable biofilters were exposed once to 0, 9.25, 18.5, 37, or 55.5 mg/L formaldehyde. Total ammonia nitrogen (TAN) and nitrite nitrogen were monitored daily before and throughout the study to quantify biofilter function. Formaldehyde concentrations ≥37 mg/L increased TAN and nitrite nitrogen concentrations, and nitrification did not recover to pre‐exposure concentrations up to 8 day postexposure. On the basis of those results, a second trial was conducted. Stable biofilters were exposed once or on four consecutive days to 9.25 or 18.5 mg/L formaldehyde. Biofilters repeatedly exposed to formaldehyde showed signs of impairment and had variable recovery relative to single exposures. Results of this study may help identify formaldehyde concentrations that can be safely applied to RAS when treating diseased fish.

Publication type Article
Publication Subtype Journal Article
Title Effects of formaldehyde on nitrification in biofilters of small‐scale recirculating systems
Series title Aquaculture Research
DOI 10.1111/are.13785
Volume 49
Issue 9
Year Published 2018
Language English
Publisher Wiley
Contributing office(s) Upper Midwest Environmental Sciences Center
Description 11 p.
First page 3207
Last page 3217
Google Analytic Metrics Metrics page
Additional publication details