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Upper Midwest Environmental Sciences Center

Determine the effect of PARASITE-S® (formalin), administered to control mortality from saprolegniasis, on the nitrogen oxidation efficiency of the biofilters of recirculating aquaculture systems (RAS) for freshwater finfish

Principal Investigator: Kim Fredricks

Impact of UMESC Science

Data from this study is intended to support label expansion for PARASITE-S® allowing for the use of the drug to control mortality due to saprolegniasis infestations in all fish rearing systems, including recirculating aquaculture systems (RAS).


A RAS is a self-contained aquaculture system used to intensively rear fish and other aquatic organisms in ecologically sustainable ways (Wik et al. 2009).  These systems are popular in areas where freshwater is limited because they recycle 90 to 99% of the water within the system (Ebeling et al. 2006, Badiola et al. 2012).  Another benefit of these systems is that they allow for greater control over water quality allowing for optimization of species specific growth conditions (Badiola et al. 2012).

In part, the success of RAS hinge upon the ability of biofilters to convert toxic ammonia compounds released into water as a waste product from fish metabolism to a safe form of nitrogen (nitrate).  The biofilters contain bacteria.  The bacteria in the genera Nitrosomonas, Nitrosococcus, Nitrospira, Nitrosolobus and Nitrosovibrio are the ammonia oxidizers.  The bacteria in the genera Nitrobacter, Nitrococcus, Nitrospira and Nitrospina are nitrite oxidizers (Hagopain and Riley, 1998).

During intensive RAS culture, fish are susceptible to pathogens resulting from high rearing densities and reuse of water.  There is a need to identify drugs that can be used in these RAS that will effectively treat diseased fish without disrupting the ability of the biofilter to convert ammonia to nitrate.  PARASITE-S® (formalin) is currently approved for use as a parasiticide for all finfish and for use as a fungicide for eggs of all finfish.  Information concerning the impact PARASITE-S® may have on a RAS biofilter function is lacking.


Determine the impact PARASITE-S® will have on the ability of the RAS biofilter to convert ammonia to nitrate.


Badiola, Maddi, Diego Mendiola, and John Bostock.  2012.  Recirculating Aquaculture Systems (RAS) analysis:  Main issues on management and future challenges.  Aquacultural Engineering.  51:  26 – 35.

Ebeling, James, Michael Timmons, and J. Bisogni.  2006.  Engineering analysis of the stoichiometry of photoautotrophic, autotrophic, and heterotrophic removal of ammonia – nitrogen in aquaculture systems.  Aquaculture. 257:  346 – 358.

Hagopain, Daniel and John Riley.  1998.  A closer look at the bacteriology of nitrification.  Aquacultural Engineering.  18:  223 – 244.

Wik, Torsten E.I., Björn T. Lindén, and Per I. Wramner.  2009.  Integrated dynamic aquaculture and wastewater treatment modeling for recirculating aquaculture systems.  Aquaculture 287:  361 – 370.

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