Abstract
There are a number of products on the market, including the Aquascape® IonGenTM system, that claim to reduce the algae content within backyard freshwater ponds by releasing small amounts of copper and zinc ions.1 These systems assure consumers that their products are entirely safe for fish. Most freshwater fish species only tolerate low amounts of copper in the water and may be sensitive to levels as low as 0.5 ppm or less.2 Studies have shown that copper may affect hematological parameters of fish, resulting in increased energy consumption to re-establish homeostasis.3 Zinc may also become toxic to fish, especially during hypoxic conditions like overwintering.4 Zinc has been found to negatively affect growth and development, morphology, and physiology of fish.5 Koi carp (Cyprinus carpio), a popular ornamental fish species, are particularly affected by high levels of heavy metals.2 A clinical case involving a koi pond in the Raleigh, North Carolina area produced clinical and laboratory evidence of toxic levels of zinc and copper in the tissues of several koi specimens. Acute heavy metal toxicity in fish causes the breakdown of gas exchange at the gills, resulting in tissue hypoxia and even death.6 The objective of this study was to determine whether or not levels of zinc and copper emitted by the IonGenTM system could pose as a health hazard for common ornamental fish. The IonGenTM apparatus was tested in a controlled environment utilizing 1500 L tanks containing approximately 1100 liters of water. Water samples were sent to Pennsylvania Animal Diagnostic Laboratory System and levels of copper and zinc were measured in two control tanks and two tanks containing the IonGenTM product over the course of 12 weeks. The results of this experiment demonstrate a statistically significant (p<0.05) increase in the levels of copper and zinc in the tanks containing the IonGenTM system, with levels of copper reaching 18.2 ppm and levels of zinc reaching 0.41 ppm. This data suggests that copper and zinc produced by the Aquascape® IonGenTM system may reach toxic and even lethal levels for some aquatic species within closed aquatic systems. These results call for better regulation of copper- and zinc- emitting commercial products labeled for maintenance of freshwater ponds, especially in areas where hypoxia during winter may exacerbate the effects of heavy metal toxicity.
Acknowledgements
The authors would like to thank Pennsylvania Animal Diagnostic Laboratory System for sample analysis and the NC State College of Veterinary Medicine for financial support.
* Presenting author
+ Student presenter
Literature Cited
1. IonGenTM System G2. Aquascape® Inc [online]. St. Charles, Illinois. Trademarked 2009. www.aquascapeinc.com/products/iongen. Accessed 1/30/17.
2. Blasiola GC. 1995. Koi: A Complete Pet Owner's Manual. New York, NY: Barron's Educational Series; 60 p.
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