Do You Have Metal Toxicity?

Published on May 1, 2010

koi_health_testingFish live in water–simple fact. Fish are dependant on the quality of this medium just as air breathing animals need clean air in order to survive and flourish. Very low levels of toxins can cause sudden mortality or allow immunosuppression leaving the individual open to secondary bacterial and or fungal infections that would not ordinarily be a threat to a healthy animal. It is imperative as hobbyists and pond maintenance contractors to address the needs of the fish and determine if they indeed have “good” water to live in.

There are myriad water quality kits on the market from simple colorimetric dropper kits to mini spectrophotometers. Most address the standard water parameters such as pH, ammonia, nitrite, hardness. These are all important to monitor on a regular basis. There are trace elements, however, in most water supplies that can be problematic to aqueous species. Water that is safe for human consumption may be toxic to fish. Fish live in the water. We merely ingest it and expel most of it. The biggest threat to the livelihood of your fish is not easily measured. Specialized equipment is necessary in order to detect very low levels of trace elements such as heavy metals that tend to accumulate in the internal organs of fish. This accumulation leads to immunosuppression. Often we see fish that are suffering from bacterial infections for no apparent reason. We often find that initial water quality is optimum but low levels of copper and/or zinc are present. Metals are most toxic in low alkalinity and pH. This allows for a higher concentration of metal to remain dissolved. The accumulation over time immunosuppresses the fish and allows the normal pathogenic bacteria to gain the upper hand leading to ulceration and possible septicemia (bacteria in the bloodstream).

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Clinical signs of heavy metal toxicity can be mortality, ulcerations, fin rot, fungal involvement, and lethargy for no discernable reason. If heavy metal toxicity is suspected it is advisable to submit samples to the appropriate laboratory for analysis. Commercially available kits are not sensitive enough to determine ppm (parts per million) to the levels necessary for an adequate diagnosis. For example, the acceptable levels of copper and zinc in soft water are .006 and .005 ppm respectively. A lab capable of atomic absorption spectroscopy analysis can detect these low levels. KOILAB can run 16 trace elements (aluminum, boron, cadmium, calcium, copper, iron, magnesium, manganese, molybdenum, nickel, phosphorus, silica, sodium, and zinc) as well as pH and hardness. As previously mentioned it is important to assess pH and hardness to determine the acceptable levels. Heavy metals are more toxic in soft water and low pH. Low levels of heavy metals might be of no consequence if your water comes from a limestone aquifer.

Sources of heavy metals vary. One of the most common is heat exchanges that have copper or bronze elements. Municipal water supplies can harbor heavy metals. As aforementioned water that is suitable for human consumption may not be safe for your pond inhabitants. Galvanized metal, zinc from roof shingles, copper supply pipes are all possible sources. Several years ago we had a case of pond liner that proved to be toxic. It turned out to be roofing liner that was permeated with zinc. Many wells have high levels of heavy metals, particularly iron. Iron oxide precipitates in the gill tissue when anaerobic water from a well is exposed to air.

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I think these issues are particularly relevant to the pond contractor and those involved with pond maintenance. The contractor should suggest to the pond owner that a “pond physical” is necessary in order to establish a baseline and determine if any adjustments are necessary to ensure the correct water quality parameters. Hardness can be manipulated as well as pH. Heavy metals can be removed with specialized filters. Chelating agents such as EDTA can be utilized as well. Many of the dechlorinating agents will remove heavy metals.

**How to Collect and Submit Samples**

Our lab requires about 100 mls of water. A drinking water bottle is a suitable container for this purpose. Drink the water or pour it out and rinse the bottle several times with the water in question. I prefer to test the pond and the source water to determine the possible cause of the contamination. Keep the water refrigerated until it can be submitted. Send samples on a cold pack to:

3831 Flat Rock Road
Watkinsville GA 30677

Include a processing fee of $75.00 per sample and contact information. Results will be e-mailed in approximately 3–4 days upon receipt of the samples. For more information contact Vicki Vaughan at 706/247-6274 or

Also see web article – Koi Lab.

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3 thoughts on “Do You Have Metal Toxicity?”

  1. pls can you send me the list of chemicals and other agent that are use in remiving heavy metals from fish pond

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