# Allopathy among plants (Cryptocoryne's in particular)



## TorontoPlantMan

Over the past 2 years in my 20 gallon tank I've experimented with numerous plants species under a wide variety of lighting (T5HO, CFL's, LED). As I've watched my plants mature and experimented with adding new plants and taking others away I've noticed two really important factors which I thought I'd share with others.

1: Cryptocoryne's grown directly beside Vallisneria species = Trouble. 

2: Cryptocoryne's/Vallisneria/Amazon Sword = Trouble

Although all my plants have started out well and grown to their full potential, especially the Cryptocoryne's and Amazon Sword, as the Vallisneria species has begun to get bigger/send more runners the Amazon Sword and Crytocoryne's which are very close to the Vallisneria species are beginning to show signs of nutrient deficiency. 

I've done everything from CO2 and ferts like Nitrogen, Potassium, Phosphorus, Trace, Iron, and Flourish, all with absolutely ZERO positive results when trying to treat the Amazon Sword and Cryptocoryne's. 

I've previously read on Aquatic Plant Central about Allopathy among plants, which was actually first presented by a member who belongs to this forum as well and is a fellow Canadian/Torontonian.

I'd like to hear about other's experiences with growing these plants among CLOSE proximity. Please expand greatly on your experiences with these plants, no short answers just to gain posts please.


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## colio

I actually had a crypt growing on top of my sword, more or less (you couldn't really see the crypt it was so buried by the giant sword). The sword plant seems to be doing well, in that it has fired off two stems and made piles of babies. Lost a few leaves though, and some browning around the edges. So maybe the crypt is taking a lot of the nutrients from the sword. 

There is coincidentally a group of small vals pretty close by, which are doing OK but not great. Firing off some runners, but not spreading like crazy or anything. Ir growing past 8 inches which is frankly very surprising for Vals (v. americana I think). 

The root system of the sword extends more than 12 inches, so I don't think any small group of plants could possibly completely deprive it of nutrients.


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## aniroc

I believe the term is "allelopathy" and it is not universally accepted as it is often difficult to distinguish from "competition" especially when resources are limited. 
Swords and crypts are both root feeders, I think it is more likely a competition for nutrient rather than a "chemical" released by one plant.
However, my own experience, awhile back I had a water sprite growing aggressively in my tank while the swords and crypts were barely surviving. I used to thin it weekly to make swim space for my fish. Not anymore. The swords are thriving now, water sprite doing poorly. I don't know why.


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## Lee_D

I find Vals to be an extremely fast growing plant in that they send out runners very rapidly. As a result, they deplete the nutrients quite quickly. I picked up some vals at an auction that I suspect had spent the summer growing in a pond. They were huge. When I put them in the tank they sent runners everywhere but the new plants never grew more than a few inches tall and quite rapidly faded in colour. Then the tank would develop large amounts of hair algae indicating a nutrient imbalance affecting the rest of the plants in the tank. I do low tech, medium light tanks.

Lee


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## TorontoPlantMan

Interestiing to see everyones experiences. I'm still convinced there is something going on between the val's and crypt's. I don't see a problem with amazon swords and crypts, just vals effecting crypts and swords.


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## Green Wet Thumb

The following article was written by a member of the Durham Region Aquarium Society and published in the August 2013 edition of _The Tropical Times_, the publication of the Sacramento Aquarium Society... (It was too big to put as a single post, so I've divided it in two...) Not directly on point, but interesting.

*My Green Wet Thumb: Allelopathy* 
Derek P.S. Tustin

I have three long-term passions in the aquarium hobby, two of which are Rainbowfish and aquatic plants. Trying to explain or justify to others why they are attractive to me is futile, so I just accept it and go on my merry way. But my other sustained passion in the hobby is research. I firmly believe that answers to most questions are out there somewhere, be it in a book, article, threads in a forum, or with a member of my local club. If we take the time to look for an answer, usually we will find it.

Now for those of you who don't keep aquatic plants, you may not realize the true frustration that this aspect of the hobby can bring. Why will my Aponogeton madagascariensis grow, but my Aponogeton distachyos won't? Why can I grow Cryptocoryne cordata but not Cryptocoryne aponogetifolia? Why Vallisneria americana but not Sagittaria sagittifolia? (I think to some degree those who have never tried to grow aquatic plants think that all aquatic horticulturists are nuts. _"How hard can it be, it's only a plant?"_) So as I always do when I have a question I want (or need) to be answered - I researched. I found possible solutions / reasons in differences in photoperiod, temperature, water conditions, nutrients, fertilizers being used, lack of CO2... in fact, pretty much all the standard problems. But I also came across another suggested cause - "allelopathy".

This past April, I attended the 2013 American Livebearer Association convention in Grand Rapids, Michigan. While livebearers are not a focus of mine, I was very interested in the opportunity to meet some fellow hobbyists, to travel with some friends from my local club, and to experience a national convention. All in all, it was a great experience, but one of the main things I came away with was a copy of Diana Walstad's book, _Ecology of the Planted Aquarium: A Practical Manual and Scientific Treatise for the Home Aquarist_. I'd been looking for a copy of this book for some time, and was able to get a copy from one of the booksellers at the convention. You see, I knew that it contained some information on allelopathy in the aquarium, and was in fact one of the few sources where it was described in depth.

As mentioned, allelopathy is one of those terms I have stumbled across, in this case while reading on why certain plants won't grow together. For those of you not familiar with it, allelopathy is a biological phenomenon whereby certain plants, algae, bacteria, coral or fungi, produce biochemicals (called allelochemicals) that affect the growth, reproduction and survival of other organisms in a local environment. This influence can either be beneficial to the other organisms (called positive allelopathy) or to their detriment (logically called negative allelopathy).

The word is derived from the Greek words "allelon" (meaning "of each other") and "pathos" (meaning "to suffer"), and was first used in 1937 by the Czech-Austrian botanist Hans Molisch in his book The Effect of Plants on Each Other. The book basically examines how biochemical interactions exist between two plants when one plant release allelochemicals that inhibit the growth of neighboring plants.

But the concept of what is now described as allelopathy wasn't discovered by Hans Molisch. Indeed, Theophrastus, a Greek philosopher from around 300 BC, noted that the presence of some plants inhibited the growth of others. 400 years later, or around the 1st century AD, both Chinese and Roman writers noted that the presence of some plants had effects on others in their vicinity.

The majority of these studies, both historic and modern, focused on terrestrial plants acting on other terrestrial plants, especially in forest and agricultural settings. After the creation of the term allelopathy, it was co-opted by zoologists to also describe biochemical interactions between both corals and sponges and the surrounding environment.

Where we stand today is that some proponents of allelopathy feel that bio-chemicals released by plants via leaves, flowers, roots, fruits and stems can affect other plants surrounding it, usually in the form of reduced seed germination and growth of any seeds that do take root. But as with all scientific theories, allelopathy has its detractors. Some feel that what is being described as allelopathy is actually resource competition between plants in the same area.

Resource competition is the process by which one plant acquires more of the available resources (such as light, nutrients and water, light) to the detriment of neighboring plants. This can occur either through exploitation (e.g. one plant growing taller to gain access to the sun and shading the competing plant), or through interference (e.g. one plant growing over another to both gain better access to light and completely blocking light from getting to the other).

That is a down and dirty, broad-strokes explanation of allelopathy, and at this point, many of you will be scratching your head and asking _"What does this have to do with aquatic horticulture?"_ As I mentioned, I was looking forward to reading Ms. Walstad's book, thinking that her section on allelopathy might provide a valuable resource in my better understanding one aspect of my aquatic plant problems.

Unfortunately, in addition to the information contained therein being presented in a very scientific manner (necessitating some intense concentration while reading), it also didn't convince me. In fact, much of what was written on allelopathy seemed somewhat ... hesitant. For example (emphasis added in all instances);

_"Allelopathy between plants *may* explain instances of a particular plant not doing well in a home aquarium."_ - page 33

_"Aquatic plants *probably* release large amounts of allelochemicals..."_ - page 40

_"Aquatic plants *apparently* release chemicals into the water that repel invertebrates."_ - page 44

To me, "may", "probably" and "apparently" are all words indicating a degree of doubt or hesitation. Yet Ms. Walstad's ends her section on allelopathy with the statement "I believe that allelopathy is rampant in the home aquaria." Her description of the phenomenon is made with reservations, yet she avows that it exists.

But the wording chosen by Ms. Walstad was not my only problem with what she was describing. At one point she writes _"For example, Amazon sword-plants, Anubias nana, Limnophila, and some Cryptocoryne thrive together in my 50 gal. However, I have not been able to grow any Vallisneria in this tank."_ I fully accept that Ms. Walstad may not have been able to successful-ly grow those plants together, but... I have. Does that mean that I am special? No, it means that something in my environment is amicable to the plants growing together. It may be different lighting, different substrate, different photoperiod, different fish, different water parameters, different frequency of water changes, different food... it short, it may be one or a number of different factors working in concert.

Now I should mention that Ms. Walstad promotes the Natural Planted Tank (NPT) method of setting up an aquarium. Essentially it is a natural planted tank containing a soil underlayer covered by gravel, where the majority of processes are naturally occurring and few water changes are required. (I should note that should this style of aquarium keeping sound attractive to you, you must research it completely before trying it. There are many who keep aquariums using this method, but in order to do so successfully, you must understand the process and why it works before trying it.) In this style of aquarium set up, maybe allelopathy becomes a factor due to the low fre-quency of water changes. But I was still not convinced that allelopathy is something that is a factor in the aquariums I keep.


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## Green Wet Thumb

So, never believing that one source is enough, I turned to the internet to see if there were any other opinions on allelopathy in the aquarium.

On the surface, the only other opinion on allelopathy in the aquarium is that offered by Tom Barr, another highly respected aquatic horticulturist. His re-sponse? _"Allelopathy is baloney, even the research has many problems demonstrating it."_(1) But beneath that is a source repeatedly cited by Mr. Barr; an article that apparently was originally published on the website of Tropica Aquarium Plants titled _"Allelopathy - Chemical Warfare Between Aquatic Plants"_ and written by Ole Pedersen, currently an Associate Professor with the Department of Biology at the University of Copenhagen. Unfortunately, the original link to that article is no longer active. Fortunately, nothing dies on the internet and a copy of the article is to be found at The Internet Archive: Wayback Machine. (2), (3)

In his article, Mr. Pedersen writes that his _"...search through the scientific literature has made [him] more skeptical about the importance of this phe-nomenon in planted aquaria..."_ He details scientific examinations made into allelopathy (providing a list of citations) and briefly examines allelopathy in the aquarium. He concludes with;

_"Hopefully, this article has provided you with sufficient knowledge so that you are naturally skeptical next time you meet these allegations on miraculous algae control by means of allelopathy. The best algae control will always be a densely planted aquarium with a limited stock of fish combined with frequent water exchange. In particular the last point probably prevents allelopathy to become important in planted aquaria since the toxic chemicals never build up to significant concentration levels and therefore the effect, if any, will never materialize."_

Mr. Pedersen focuses on the potential for allelopathy to control algae in the aquarium, but does not really address the allelopathic effects of one aquarium plant on another, such as Ms. Walstad addresses when she discusses Vallisneria species not growing in the presence of other aquatic plants. Still, he does address that frequent water changes would prevent the buildup of allelochemicals, and this holds true for one plant's allelochemicals affecting another plant just as well as for one plant's allelochemicals effecting algae.

Allelopathy no doubt exists in nature. But nothing controls nature, and we do control our aquariums. No matter how large or how small, we can only recreate a portion of nature in our home aquariums. Allelochemicals may be released by our aquarium plants, but it is highly unlikely that the effects are truly noticeable over a short period of time, especially when water changes are done. Further, the combinations of lighting, nutrients, stocking (both flora and fauna), photoperiod, choice of fertilization, choice of other additives, filtration, heating, substrate and water parameters is endless. No two tanks will ever be exactly identical, and this makes the identification of problems present in one tank but not another difficult to identify.

No doubt scientific research into allelopathy will continue in the years to come, but for now, for the majority of us, allelopathy is something interesting to know about, but not something we need to do something or worry specifically about.

On a final note, while I may have been somewhat critical of Ms. Walstad's chapter on allelopathy, in its entirety Ecology of the Planted Aquarium is an excellent resource. It is very technical, but should you make an effort to read it you will find it to be an invaluable resource.

(1) http://www.aquariacentral.com/forums/archive/index.php/t-239468.html 
(2) http://web.archive.org/web/20061125...article_fullscreen.asp?type=aquaristic&id=531 
(3) http://web.archive.org/web/20061125...article_fullscreen.asp?type=aquaristic&id=532


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## TorontoPlantMan

Green Wet Thumb said:


> The following article was written by a member of the Durham Region Aquarium Society and published in the August 2013 edition of _The Tropical Times_, the publication of the Sacramento Aquarium Society... (It was too big to put as a single post, so I've divided it in two...) Not directly on point, but interesting.


Very interesting read, I really liked that and thank you for your contribution. It's too bad that Mr. Pedersen focuses on allelopathy to combat algae instead of allelopathy among growing plants together. All in all great read though


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## jimmyjam

I havent had many issues with my plants yet aside from big LAromatica out reaching for light over a few smaller plants. With that being said, I dont keep many crypts, Vals or swords, or many super heavy root feeders. I think it ultimately it comes down to natural selection/survival of the fittest. Heavy root feeders/ fast growers will outcompete a similar plant with slower growth. I see it similar to the ultimate battle with Algae in a aquascape, we are trying to create the best situation for our aquatic plants to out compete the algae. 

And great read by the way guys.


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