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Are Pond Ionizers Safe? You be the judge.

Certain manufacturers of Pond equipment decided to borrow a technology from the Swimming Pool industry and, with maybe some minor tweaks, promote it as an exciting breakthrough in controlling Pond algae. Presenting the IONIZER!

Through the controlled release of Copper, Zinc and Silver ions into the pond’s water column, algae growth can be controlled and in many cases eliminated. This, on the surface, is great news for Pondkeepers. No longer is it necessary to use expensive and hard-to-correctly-measure chemicals. Just set the Ionizer to the desired level and algae disappears.

Sounds great! However, there is more to be considered than just what the advertisements claim. What are the other potential and likely results from use of this device that the manufacturers are not telling us?

Let’s look at some of the manufacturers’ claims as regards Ionizers.

Company #1
  • Destroys Bacteria
  • Kills Algae
  • Reduces chemical cost
  • Eliminates chemical odors
  • Reduces maintenance
  • Environmentally Friendly
  • Costs pennies per month
  • Helps reduce filtration
  • Fish safe
  • Includes 2" T Fitting

Company #2
  • Safe for fish and plants
  • Low maintenance
  • Clears water without the use of harsh chemicals
  • Easily installed in any new or existing water feature
  • Treats ponds up to 25,000 gallons
  • Level of mineralization is controlled by the LED panel
  • Cast mineral anodes are self-cleaning
  • 1 year warranty
Company #3
  • Drastically reduces pond maintenance
  • Crystal clear water without the use of chemicals
  • Eliminates unsightly water conditions
  • Simple to install
  • Safe for fish and plants
  • Not toxic to animals that may drink from the pond
  • Energy efficient (less than $ 1 a month in electricity cost)
  • Treats ponds up to 25,000 gallons
Understandably, the first concern of a Pondkeeper is whether a product or treatment is safe for fish. All three (3) of these manufacturers declare that the (proper) use of this device is safe for fish. Let’s take a closer look at this claim.

All Three (3) manufacturers include test strips for monitoring Copper levels with Two (2) of the manufacturers recommending maximum Copper levels at 0.25 mg/L and the remaining manufacturer recommending 0.30 mg/L as the maximum level of Copper.

Copper is a heavy metal and in low concentrations can be toxic. In addition, like other heavy metals, such as Mercury, it is a bio-accumulate. This means that once it is ingested by an organism it remains in that organism for an extended period of time, in many cases, for life. Any additional ingestion only increases the level that is already present in the organism until eventually a certain level of toxicity is reached. For terrestrial organisms, this level is determined primarily by the ingestion of food and water, but for aquatic organisms, if the Copper is in suspension as ions, it may be ingested during the respiration process also, as is the case with fis juvenile amphibians, certain insect larvae, true aquatic invertebrates and bacteria as well as the target taxa of algae. In the case of fish, it causes increased mucous production on the skin and the gills where it eventually interferes with the respiration process by blocking the absorption of Oxygen.

In assessing the potential toxicity of any substance to any organism, two (2) distinct levels must be determined, acute (immediate short term) and chronic (long term). Heavy metals have long been known to play an important beneficial and cricial role in animal and plant physiology, but at levels so low that they are undetectable by standard testing.

Considerably greater attention has been given, in recent years, to the effect of Heavy Metals and other chemical compounds on the environment. Research is ongoing in both the public and private sector. This research has resulted in some universally accepted toxicity levels as regards Heavy Metals.

The focus here will be on Copper. Copper, after Mercury, is the most toxic of the Heavy Metals. Copper’s toxicity is greatly influenced by water Hardness and pH. As water Hardness and ph increase, the toxicity of Copper is reduced. Here is an example of a couple of simple formulae that are used to define the accepted level of Copper in fresh water.

Maximum Copper levels (in micrograms) at any time—0.094(hardness)+2 (where water Hardness is reported as mg/L CaCO3.

30 day average Copper levels (in micrograms)—0.04 average hardness (where water Hardness is reported as mg/L CaCO3.

(Environmental Protection Division, Ministry of Environment, Government of British Columbia)

Note - There are other formulas used by different government entities worldwide, but the final accepted levels of Copper vary by only a few micrograms.

Using these two (2) formulae, in water with a Hardness of 120 ppm for example, we find the recommended Copper levels to be 13 micrograms/L at any one time and the 30 day average should not exceed 5 micrograms/L Knowing that one milligram equals 1000 micrograms, these results expressed in mg/L would be 0.013 mg/L and 0.05 mg/L. These results appear to be on the conservative side, but considering the fact that some aquatic organisms have a very low tolerance to Copper, these formulae are quite appropriate.

These are the Metal Safe Limit levels as defined in the Textbook of Fish Health: Copper 0.014mg/l More toxic in soft water; Zinc exacerbates toxicity; Combined both are dangerous; Zinc 0.01mg/l Synergistic with copper; 0.15mg/l In hard Water; Cadmium 0.03mg/l; Chromium 0.10mg/l; Lead 0.01mg/l In soft Water; 4.00mg/l In hard Water; Silver 0.03mg/l (mg/l is the same as ppm).

The author was unable to find any scientifically set copper toxicity levels for Koi, but several anecdotal sources were found that stated that Koi begin to show copper toxicity at 0.03 ppm along with the copper toxicity level for Koi at 0.3 ppm., which is at or extremely close to the Maximum levels suggested by the manufacturers of these devices. It should be stressed that no scientific studies were found that substantiated these levels. In fact, one study reported that Koi fry were unaffected by Copper levels of 1.00 mg/L.

It is important, however, to know the signs and symptoms of Copper toxicity in Koi. One of the earliest effects of too much copper is apparent fish hypoxia, the loss of ability to use oxygen. Common symptoms of initial acute toxicity are fish gasping, disoriented (ataxic) at the surface, due to copper's hemolytic (blood cell splitting) and mucus-producing effects. Copper is a proteinaceous precipitant; that is, it causes your fish to produce more mucus. This may aid the in the suffocation or sloughing off of parasites, but also interferes with respiration through their skin and gills.

Of greater concern is the previously mentioned fact that all heavy metals are bio-accumulates. This accumulation leads to immunosuppression. Fish are often observed suffering from bacterial infections for no apparent reason. 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).

In eco-system ponds, along with the fish, the toxicity of copper to all other aquatic organisms is of equal importance. Considerably more data is available on the effects of copper on fresh water fauna due to the fact that they are present in every natural waterway and their numbers and diversity are prime indicators of the health of any aquatic eco-system.

Copper is extremely toxic to most invertebrates and the juvenile forms of most amphibians.

"Northern leopard frogs (Rana pipiens) were exposed to environmentally relevant concentrations of copper in water (control and 5, 25, and 100 microg/L, as CuSO4) in a static renewal system for 154 d from posthatch stage to metamorphosis. Tadpole survival, swimming performance, percent metamorphosis, time to metamorphosis, and survival during and time required for tail resorption were negatively affected in the 100-microg/L treatment."

-Adverse effects of chronic copper exposure in larval northern leopard frogs (Rana pipiens).

Chen TH, Gross JA, Karasov WH.

Available toxicity data on amphibians indicate copper 96 h LC50 values calculated in tadpoles ranged from 0.04 to 5.38 mg/L. Studies of other aquatic organisms show 96 h LC50 values ranging from 0.06 to 6.68 mg/L.

Representative toxicity levels for some other fresh water organisms are-

Most snails – 8 - 41 micrograms/L; Cladocerans (including Daphnia) 5 - 213 micrograms/L; Amphipods 8 - 87 micrograms/L

Although the Mayfly is fairly sensitive to Copper, the majority of insects that have aquatic larval stages are tolerant, most notable Damselflies and Dragonflies, which are always expected visitors to any aquatic venue. These Odonates have the ability to store heavy metals in their exoskeletons where it remains harmless.

The inhibition, reduction or elimination of any member group of the aquatic food chain will have negative effects on the overall health of the eco-system to a lesser or greater degree depending on which species are residents of that particular eco-system and their relative position in the food web.. Nevertheless, any negative effect on an aquatic eco-system’s food chain and/or diversity will have deleterious effects on the entire system.

The only organisms that have not been discussed are the bacteria, in particular, the nitrifying bacteria. The results of studies on the toxic effects of Copper are quite surprising. Copper and Zinc appear to be the least toxic of the metals tested. Copper, at low levels, actually stimulates activity in Nitrobacter. At levels up to 0 50 mg/L the Copper ion has no toxic effect on Nitrobacter. Instead, the stimulatory effect is readily apparent......Apparently. at 0 50 mg/L Copper has not reached the cross-over point where a chemical shows neither stimulatory nor inhibitory effects. This, unfortunately, is not true of Nitrosomonas. Growth of Nitrosomonas is greatly inhibited (about 60%) by Copper concentrations of 0.20 ppm.

Growth of Nitrosomonas europaea in batch and continuous culture (Skinner & Walker 1960)
Copper was also found to be one of the most toxic metals to heterotrophic bacteria in aquatic environments.
Sadly, company #1 is partially correct in claiming that their ionizer "destroys bacteria".

In conclusion, based on the above data, we arrive at these facts-

-Ionizers can indeed control and, in some instances, eliminate many species of algae.

-Within the manufacturers’ suggested range of use, 0 – 25/30 mg/L, neither Koi or Goldfish should exhibit any immediate effects of Copper toxicity. It has been shown that Koi fry can tolerate levels of 1.00 mg/L. Due to lack of any meaningful research, long term (chronic) effects are unknown.

-Copper at low levels is extremely toxic to aquatic stages of most amphibians.

-Most microorganisms exhibit toxic effects of Copper at extremely low levels and, where mortality does not occur, the effects are compounded in second generations.

-The effects of relatively low (.20 ppm) Copper levels on one of the main species involved in Nitrogen conversion has the potential to cause major problems in the form of Ammonia spikes.

Considering the whole picture regarding the impact that an Ionizer may have on an aquatic eco-system, this author has no intention of availing himself of its use. There are other effective and absolutely safe ways of controlling and/or eliminating algae. You, the reader, may feel differently. After all, it’s your Pond and your fish.

You be the judge!

Update Nov. 29, 2012

There has long been a dearth of information regarding the toxicity level of Copper in Koi (Cyprinus carpio). Finally some figures are being established by scientific research.
According to a recent research paper (Dietary tryptophan changes serum stress markers, enzyme activity, and ions concentration of wild common carp Cyprinus carpio exposed to ambient copper
Fish Physiology and Biochemistry (2012) 38: 1419-1426 , October 01, 2012

By Hoseini, Seyyed Morteza; Hosseini, Seyed Abbas; Soudagar, Mohammad), Carp exposed to 10 mg/L Copper exhibited mortality rates of 21.7 ± 7.6 % at 120 hours and 61.7 ± 10.4 % at 168 hours. Although this level of Copper is 40 times the (claimed) maximum levels generated by ionizers, I feel that it is safe to infer, because Cu is a bio-accumulate, that depending on the usage (level settings and duration of these settings) of ionizers, that Koi/Carp would exhibit physiological and behavioral signs of toxicity much quicker than was originally thought….months instead of years. Hopefully more definitive figures will be forthcoming.


Update July 8, 2014

In this recent research paper - Acute effect of copper exposure on serum biochemical characteristics of common carp (Cyprinus carpio L.), Melika Ghelichpour the effects of low level exposure to Copper were markedly detectable.
"Effects of ambient copper was investigated on serum stress markers, sodium and enzyme levels in Common carp (Cyprinus carpio L.) over a 14-d exposure period. Fish were exposed to 0, 25 and 100 microg L-1 copper (as copper sulfate) and blood was sampled at 0, 3, 7 and 14 d after exposure. Serum profile was significantly affected by copper concentration, sampling time and their interaction. Increase in serum levels of cortisol, glucose, alanine aminotransferase and aspartate aminotransferase and decrease in serum sodium levels were observed in both copper-exposed groups, 3 d after copper exposure, which lasted until the end of the experiment. It is concluded that copper exposure causes stress response and sodium loss in common carp. Likewise alanine aminotransferase and aspartate aminotransferase increase after exposure which might be as results of either tissue damage or stress."
Note: Copper Sulfate readily disassociates in water producing Copper ions. The physiological effects would be the same with an ionizer.
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