Effects of formalin, chemotherapeutic treatments on biofilter efficiency in a marine recirculating fish farming system

N. Keck, G. Blanc-2002

Aquatic Living Resources, 15(6): 361-370  (from ISI Current Contents)

Abstract:
Formalin (a 33-38% aqueous formaldehyde solution) is currently used for bath treatments to control ectoparasitic infections of fish. Its effects on nitrification were evaluated in a semi-closed pilot scale saltwater recirculating turbot culture system. Tested treatments included I It static exposure to 20, 30, 40, 50, 60, 70, 90 mg l(-1) formaldehyde without flushing, and long-term (i.e., 2, 4 and 6 h) exposures with constant 60 mg 171 formaldehyde in a recirculating system. Formaldehyde has no apparent effect on the ammonia oxidative bacterial community. However, a significant effect on nitrite oxidation was observed in 1. h static exposures of concentrations higher than 40 mg l(-1), and in recirculating system exposures of 60 mg l(-1) formaldehyde for more than 4 h. Repeated treatments may be hazardous for nitrifying bacteria, which could induce an increase in nitrite concentration. Nitrite concentrations should be monitored when treatments are repeated or when they last a long time in recirculating aquaculture systems.

(Ecole Natl. Vet., INRA Envn. Umr. 1035, Route Gachet, Atlanpole Chantrerie, BP 40706, F-44087, Nantes, France, e-mail of G. Blanc: blanc@vet-nantes.fr)

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