DOI: 10.5061/dryad.vhhmgqnq5
title: Copper and zinc generated by the Aquascape IonGen pond clarifier system can be detrimental to koi (Cyprinus carpio) health

description: BackgroundCopper is frequently used as an algicide, and copper ion
 generators such as the Aquascape IonGen claim to be safe for use in
 systems containing fish. In 2012, a die-off of koi (Cyprinus carpio) in a
 pond in Raleigh, North Carolina, occurred after the IonGen was added to
 the system.MethodsPhysical and postmortem examinations suggested that
 heavy metal toxicity was the likely cause of morbidity and mortality. This
 was supported by a heavy metal screening of the owners’ pond. Additional
 experiments were performed to determine if the IonGen produced toxic
 levels of copper and zinc.ResultsThe tank containing the IonGen had higher
 concentrations of copper and zinc, and copper levels exceeded those
 associated with toxicity in both hard and soft water.ConclusionThe results
 of this study indicate that ion generators might not be safe for fish, and
 copper should only be used as an algicide if concentrations are closely
 monitored.
description: Water quality samples and liver tissue from one of the deceased
 fish were sent to the Pennsylvania Animal Diagnostic Laboratory in Kennett
 Square, Pennsylvania, for analysis.  To determine whether the
 IonGen<sup>TM</sup> Cu ion generator used in the backyard pond
 could generate toxic levels of heavy metals, an experiment was carried out
 to measure the output of Cu, Zn, and silver (Ag) by the
 IonGen<sup>TM</sup> over time. One 1130 L tank was fitted with
 an IonGen<sup>TM</sup> and another 1130 L tank without the
 IonGen<sup>TM</sup> (control). All other parameters between
 the tanks were identical. Water samples were collected from both tanks
 before the addition of the IonGen<sup>TM</sup>, and then
 weekly for 12 weeks. The samples were sent to the Pennsylvania Animal
 Diagnostic Laboratory for analysis. The water samples were analysed for
 Cu, Zn, and Ag, using NexION 300D ICP-MS (Perkin Elmer, Shelton,
 Connecticut, US) by the PADLS New Bolton Centre Toxicology Laboratory,
 University of Pennsylvania, School of Veterinary Medicine, Kennett Square,
 PA.  The analytical standards were purchased from SCP (Champlain, New
 York, US) and trace metal grade nitric acid was purchased from Fisher
 Scientific (Pittsburgh, PA, US).  All dilutions were done using in-house
 deionized water (≥18 MO cm) obtained from a Millipore water purification
 system. Three
 millilitre (mL) portions of the water samples were placed in Teflon PFA
 vials (Savillex, Minnetonka, Minnesota, US) and digested overnight at
 70<sup>0</sup>C with 1 mL of concentrated nitric acid.  The
 digested samples were cooled to room temperature and diluted with
 deionized water to a final volume of 10.0 mL after addition of 4 internal
 standards with a final concentration of 20 ppb
 (<sup>74</sup>Germanium, <sup>115</sup>Indium,
 <sup>89</sup>Yttrium, <sup>159</sup>Terbium). 
 Silver was determined by standard mode whereas kinetic<em style="font-weight:bold;font-style:normal;"> energy
 discrimination</em> (KED) mode using helium as the collision gas was
 used to analyse Cu and Zn. To ensure the proper instrument operation and
 accuracy of the results, standard curves were generated for all three
 elements of interest.  All final concentrations were reported in parts per
 million (ppm) on a wet weight basis. Method detection limits for Cu, Ag,
 and Zn were established at 0.005 ppm, 0.001 ppm, and 0.1 ppm,
 respectively, in the water samples. Eight of the samples were analysed
 in duplicate with the values within 20% of each other for all three
 elements.  Water standard reference material (1643e) with certified
 mineral values from the National Institute of Standards and Technology
 (NIST, Gaithersburg, MD, US) was analysed with each batch of
 samples.