In a classic example of science telling us what we already know, a scientist in the US has found that copper sulphate can be used as an effective treatment of Ichthyophthirius multifiliis - more commonly known as whitespot or ‘Ich'.
David Straus, an Aquatic toxicologist with the US Department of Agriculture's Agricultural Research Service (ARS), found that copper sulphate was an effective method to control both Ich in catfish and a fungus - Saprolegnia - on catfish eggs.
Ich is considered the most prevalent parasites worldwide in ornamental fish, baitfish and food fish, and although it is less common in U.S. aquaculture due to their management techniques, when it occurs, it can kill all the fish in a pond or raceway. It is calculated that Ich was directly responsible for $1.2 million in losses to the catfish industry in 2003.
So why has this made the news? Most hobbyists already know that copper sulphate works on Ich, but officially the US government doesn’t. Regulations in the US have been put on hold whilst Straus conducts his research.
At present copper sulphate is not currently approved by the U.S. Food and Drug Administration for therapeutic use in aquaculture but only as a treatment. The chemical is approved by the U.S. Environmental Protection Agency for use as an algicide and molluscicide.
Fish farmers can also use copper sulphate to control cyanobacteria and control snails that transmit parasitic flatworms to fish.
However a number of forums are sceptical about the efficacy and safety of using constant low levels of copper sulphate as a prophylactic; warning that it may kill more fish than it saves as well as having extremely toxic effects on freshwater invertebrates and some plants.
Coincidently, Straus is being sponsored by Freeport-McMoRan Copper and Gold of Phoenix, Arizona, to obtain FDA approval to use copper sulphate as a treatment for Ich in earthen production ponds and as a fungicide on eggs in catfish hatcheries.
"All technical sections are complete for the approval for Ich in catfish except for the environmental safety. We plan to resubmit the environmental assessment to the FDA by the end of the year with the additional information the agency requested," says Straus.