Be on Guard Against Copper and Zinc Poisoning in Koi Keeping

I believe none of you will be surprised by this: copper and zinc in the water will kill koi. Of course, this is not news to me either. What I mean is, before you heard the @#@163@#@ about a copper-connected heater releasing a large amount of copper into the water and thus killing all the koi, had you ever thought that copper and zinc could kill your koi? Perhaps many of us have not yet heard such a story. Before telling you these things, let me first review some of my own history.

Of course, I have been keeping koi for quite a long time. I use a microscope to identify parasites and then carry out appropriate treatment. The reason for doing this is: I live in northern Virginia, and I do not heat my pond. However, every spring, the koi in my pond always break out with disease. Year after year it is the same. When the situation occurs, I use the microscope to observe the condition and call on good friends to help deal with the sick koi.

When I started keeping koi, the density of koi in the pond was a bit high. But after a period of upgrades, the density of koi in the pond had already become very low.

In the summer season, I change the water in the pond every other day. Every day I add a settling agent to the large pond. I even change the water in the pond in winter. The filtration systems of my two ponds are twice the manufacturer's standard.

Despite the above measures, the same thing always happens every spring... koi tormented by disease. The disease outbreak this spring was even worse than in previous years. During a water change in February of this year, a Five-color koi floated to the surface and died. This Five-color had been treated in September of last year for an unidentified ulcer disease that occurred on the gill cover. At that time, when I and several of my friends examined it with a microscope, we found nothing abnormal. In short, that Five-color appeared to have been cured. It was later returned to the pond. But during a period in December of last year, the temperature was on the high side, causing the green algae in the water to multiply too quickly. Until March of this year, I was unable to clearly observe the koi in the pond. To make a long story short, that Five-color koi was the first fish to pass away in 2007. By March, I saw that the old problem among the koi in the pond had recurred. What was annoying was that toads spawned in both ponds, and I found anchor worms on several koi. Therefore, I medicated both ponds to kill the parasites. Even so, the koi's condition became more and more serious. I once again observed scrape samples with a microscope, and still found nothing abnormal. At the end of March, the temperature dropped for several days and then rose again. The toads spawned in the pond again. There was reason to believe that anchor worms were behind it, because an anchor worm infestation had already been found once before. Under the microscope it seemed there were anchor worms, so the whole pond was treated for parasites once again.

The koi's condition continued to worsen. I began treating the koi for ulcer disease. Some koi were treated with potassium permanganate. My friends and I believed there were bacteria in the pond, so some fish were also injected with Baytril. By this time, several koi had already died. I was already confused and could not even tell exactly which fish had died.

At this point, my friends suggested testing for SVC and KHV. But the symptoms did not match. Exhausted, I had already begun to consider shutting down the pond. After several months of struggle, I asked myself whether I had the ability and the mental capacity to continue keeping koi. I asked myself these questions countless times: Is the ammonia concentration normal? Is the filtration system clean?

Looking back, I once again considered the SVC virus. If the fish and water samples sent to the quarantine department tested positive, then the EPA (United States Environmental Protection Agency) would immediately come to destroy all the koi and bury all the ponds.

In short, after discussing it with friends, I decided to let the quarantine department test samples of the fish and water, because by this time my best koi had already died. By the way, all of this happened while the pH of the pond water was fixed at 9.1. I sent out samples of the fish, the pond water, and the tap water for testing. The test results were mixed: no unusual bacteria or viruses were found. However, copper and zinc were found in the water samples. Keep in mind that the levels of copper and zinc did not exceed the standard for making people sick. But the same levels of copper and zinc were enough to destroy the immune systems of the koi. In this environment, any bacteria would make my beloved koi sick and then kill them. Although I used every kind of antibiotic, I could not bring my beloved koi back from the dead. Without an immune system, a sick koi cannot be cured.

I now use Novaqua (a water treatment agent used to bind heavy metals in the water, including copper and zinc, and render them non-toxic) to treat the pond's incoming water. The next thing I need to do is find out the source of the copper and zinc in the water, whether it seeps in from the soil or comes from the tap water.