Pond Magnet Foolishness

Do magnets really have a mystical positive effect on pond water chemistry?

by Brian Dunning

Filed under Consumer Ripoffs, Paranormal

Skeptoid #07
November 14, 2006
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Also available in Japanese | Russian

With a net in one hand and a pH testing kit in the other, let's wade into the murky waters of pond chemistry to test the latest fad in koi pond maintenance: magnets.

I was visiting my cousin up in Portland Oregon, and he showed me his cool koi pond. Being a koi pond guy myself, we compared notes on filter equipment, water testing, plant types, and all the usual stuff. His main filter pipe had a group of powerful magnets arrayed around it, which was something I hadn't seen before. I'm no super expert on ponds, so I guessed that maybe it was doing something like grabbing out metal filings from the pump. I asked him what the magnets were for, and he wasn't sure, but it was something to do with water chemistry. Right away, my radar went up. Unless there were significant amounts of iron, nickel, or cobalt in his water that required being magnetically held against the side of the pipe, there's really no physical way for the magnets to have any effect on anything in the water.

My cousin's friend at the pond store had recommended that he install the magnets, and he'd followed her expert recommendation. After all, he had no reason to doubt her suggestions. At my urging, he called her up to ask what the heck the magnets were supposed to do. She hemmed and hawed, said something about water clarity or chemistry or algae, and finally confessed that she had no idea, and that it was just a standard thing that a lot of pond owners do. The magnets were pretty expensive, so it wasn't surprising that a pond store would push them.

So I turned to the Internet, as I often do in times of need. It didn't take much searching to find the standard claim about magnets and ponds, and it has to do with algae growth. The claim is that magnets, mounted inline along any of the pipes, improve water clarity by altering iron alignment in free-floating algae, thus inhibiting photosynthesis. I also found one or two references to reducing lime scale build-up inside the pipes, but since this claim didn't even pretend to suggest a mechanism that might produce this effect, I discounted it. Lime scale is calcium carbonate. It contains none of the three magnetic elements and is thus completely unaffected by magnets. That claim pretty much busts itself, no help from me needed.

So what about this reduction of algae? The claim is that the algae will be reduced because its photosynthesis will be inhibited, due to the realignment of its iron. This is a fairly common type of claim. It makes no sense, but because it uses common scientific-sounding words, many people will simply accept it at face value without questioning it. My cousin's friend at the pond store did, and when she repeated it to my cousin, he did too. I even accepted it when he told me, albeit tentatively, pending some kind of reasonable explanation.

Here are the two problems with this claim. Number one, photosynthesis is a chemical reaction among carbohydrates. Iron is not involved. The presence of iron would neither hinder nor help photosynthesis. The magnetic orientation of any iron molecules nearby is not relevant. Realigning iron magnetically has no bearing on photosynthesis, and will not harm a plant in any way. Number two, iron, which is found in human blood hemoglobin, is not present in chlorophyll or in the other proteins involved in plant photosynthesis. Although I've never spent the time to wave a magnet past a plant several times a day, I'd be awfully surprised if that plant's photosynthesis stopped and it died as a result.

Another problem with this claim is the concept that briefly passing a non-magnetic object through a magnetic field will leave it altered after the magnet is removed. This is like turning the light in a room on then off again, and expecting the furniture to be somehow residually contaminated with light. Electromagnetic radiation doesn't work that way.

I should mention that when I set out to research this claim, I didn't merely gather enough information to shoot the claim down and then quit. I did make a good effort to find research supporting the effects of magnets on algae. But, since there are no plausible claims, there has never really been anything for anyone to test. However, I did find something close. In 2005, the Woods Hole Oceanographic Institute announced the results of research they'd done on certain bacteria that are known to carry magnetic crystals. These are called magnetotactic bacteria. In 1970, magnetotactic bacteria were also discovered in the Southern Hemisphere whose magnetic crystals were flipped around. The purpose of these tiny internal compasses has never been known, but since the 1970 discovery, the working hypothesis has been that they use the compasses to help navigate either up or down to find water with the best oxygen concentration. This would be consistent with the need for the polarity to be reversed in the Southern Hemisphere.

Alas for the pond magnet manufacturers, Woods Hole's research found that north-polarity and south-polarity bacteria are both found intermixed in both hemispheres, and also that there are numerous individuals who lack the crystals completely. All three types of bacteria navigate equally well to the water depths with the most desirable oxygen levels. The conclusion of the research is that the purpose of the magnetic crystals remains unknown, but it's clear that its reversal or even its total lack makes no difference to the health or life cycle of the bacteria. And, once the bar magnet was removed from the microscope slide, the magnetotactic bacteria realigned themselves normally with the earth's magnetic field, according to the polarity of each. There were no residual effects of having been briefly placed near a magnet.

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I recommend that you do your own research, or at least ask for a reasonable explanation, when a salesman offers you a product that claims to accomplish something far fetched or contrary to your understanding of the laws of nature.

Brian Dunning

© 2006 Skeptoid Media Copyright information

References & Further Reading

Blakemore, R., Frankel, R., Kalmijn, A. "South-seeking magnetotactic bacteria in the Southern Hemisphere." Nature. 24 Jul. 1980, Volume 286, Number 5771: 384-385.

Buttner, J., Soderberg, R., Terlizzi, D. "An Introduction to Water Chemistry in Freshwater Aquaculture." The Aquaculture Network Information Center (AquaNIC). The Aquaculture Network Information Center (AquaNIC), 1 Jan. 1993. Web. 14 Nov. 2006. <http://aquanic.org/publicat/usda_rac/efs/nrac/nrac170.pdf>

Fletcher, N. The Ultimate Koi. Lydney, Gloucestershire: Ringpress Books Ltd, 1999. 168.

Murata, N. "Effect of magnetism on the growth of Dunaliella Salina." Research in photosynthesis: proceedings of the IXth International Congress. 30 Aug. 1992, Volume III: 87-90.

Schüler, D. Magnetoreception and Magnetosomes in Bacteria. New York: Springer-Verlag, 2007. 2-5.

Skomal, G. Freshwater Aquarium: Your Happy Healthy Pet. Hoboken, NJ: Wiley Publishing, 2005. 43.

Reference this article:
Dunning, B. "Pond Magnet Foolishness." Skeptoid Podcast. Skeptoid Media, 14 Nov 2006. Web. 6 Oct 2015. <http://skeptoid.com/episodes/4007>


10 most recent comments | Show all 14 comments

Clearly, the only way to resolve this would be to perform a controlled experiment using several ponds containing pond magnets and several others not containing magnets. If the magnets decrease algae growth then maybe this is worth talking about.
This being said, I can imagine how a magnet might affect algae growth. For example, I know that in ocean water, iron is often limiting. When you add iron to the ocean water you get a massive algal bloom. This may also be a factor in freshwater ponds as well.
I also remember, as a child, that when I ran a magnet through the sandbox I would obtain a lot of iron attached to the magnet, suggesting that magnets can sequester iron. Putting these two observations you might hypothesize that a magnet in a pond could act as an iron sequestration device, preventing soluble iron from being utilized by the algae. I think this experiment would be worth doing, but I would be careful to totally rule out that the pond magnets have no effect without first doing that simple experiment. At the same time you are right to question it without the vendors doing that experiment themselves.

Chris Gault, Charleston, SC
March 3, 2008 9:17am

The lime scale issue is more complicated than Brian suggests. Lime scale build-up has been reduced in some empirical studies in which water was altered by a magnetic field. Though the mechanism is not fully undertood, it is premature to dismiss this effect.

Some references:
Magnetic Water Treatment, JMD Coey, S Cass - Journal of Magnetism and Magnetic Materials, 2000

Magnetic water treatment for scale prevention, C Gabrielli, R Jaouhari, G Maurin, M Keddam - Water Research, 2001

Effectiveness of magnetic water treatment in suppressing calcium carbonate scale deposition, D Hasson, D Bramson - Industrial & Engineering Chemistry Process Design and …, 1985

Marek Petrik, Amherst, MA
April 4, 2008 7:17am

Hi, I have a large garden pond and use a U.V light which makes my water clear, But when this happens I seem to get a lot of Blanket weed, So when I purchased a magnet which is on the inlet pipe I dont get blanket weed so it must work thanks

Gary Anderson, Liverpool, UK
August 5, 2008 10:07am

How can a light make it clear AND covered with algae?

Joseph Bozeman, Norman
August 6, 2009 6:32pm

> Another problem with this claim
> is the concept that briefly
> passing a non-magnetic object
> through a magnetic field will
> leave it altered after the magnet
> is removed.

Define "non-magnetic"; (MRI works for example on "non-magnetic" material by applying a strong magnetic field).

Another thing to consider: As soon as there is a magnetic field, there is an electric field (Maxwell's equations): So - the material would have to be "non-electric" too - which I guess is even harder to define (they all have a dielectric constant,...)

The point I wanna make: The argument is nonsense because of the definition of "non-magnetic" not being supplied. And for magnetic materials, the argument is certainly not true - otherwise your harddisk would not work...

Sir Mammut, World
August 30, 2010 1:38pm

watching those lovely MIT physics lectures would clear those persistent problems up guys. They are about the best you can see on the net

Henk V., sydney, Australia
September 1, 2011 5:20am

I'd like to enlighten your article with some evidence that will have be quite "sciency." Although not directly present chlorophyll, iron serves essential metabolic functions in photosynthetic electron transport, respiratory electron transport, nitrate and nitrite reduction, sulfate reduction, dinitrogen fixation, and detoxification of reactive oxygen species. Iron is directly involved in photosynthetic electron transport via its involvement in both cytochromes and iron/sulfur centers. (Andersen 2005 “Algal Culturing Techniques”) In short, iron is present and needed in the photosynthetic process.

Furthermore you state that “briefly passing a non-magnetic object through a magnetic field will leave it altered after the magnet is removed” is erroneous in explaining algal growth. As a matter of fact, this is quite true. Algal cells have shown increased growth and metabolic functions after being exposed to a magnetic field and then being removed. Once removed, the cells still show increased cellular activity. (Small et al. 2012 “Effects of static magnetic fields on the growth, photosynthesis and ultrastructure of Chlorella kessleri”)

There are a host of other research papers that show the effects of magnetic effects on the growth of several algal species. Granted, many of them have been published since the posting of your article. What has been seen is that low doses of electromagnetic radiation (10-15mT) effectively quadruple algal growth rates.

Jeff Z, Mobile, AL
November 28, 2012 10:51am

Jeff, can you re read your comment?

Mud, At virtually missing point, NSW, OZ,
November 29, 2012 4:25am

I had a terrible algae problem in my pond and could not see the bottom.
10 days after placing magnets I removed from an old hard drive in the water exhaust stream all algae sank to the bottom of the pond and the water was crystal clear.

Glenfriede, Selma AL
October 23, 2014 3:27pm

Glenfriede some of the metals in rare earth magnets are quiet toxic so you may have just poisoned the algae.

Peter, newcastle
September 8, 2015 6:46pm

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