# Interested to hear people's views on how providing unlimited nutrients helps control algae?



## neil1973 (13 Mar 2015)

The question: How does EI, or any other method where the aim is to keep all nutrients at levels that are not limiting, help control algae growth?

I have used such approaches with good results as have many others. I think most would agree that the basic principle is that all nutrients (including CO2) are provided at levels that are sufficiently high as not to limit growth. In such a situation light will become the limiting factor in terms of photosynthesis and plant growth. The result of such an environment is that plants grow quickly and are strong and healthy. It is generally accepted that where there is a sufficient quantity of plants that are healthy and are growing well then algae growth is limited. I have seen this as have many others. What I am interested in is why does this happen?

I've seen a number of mechanisms suggested over the years that i'll try and summarise here:

·  The healthy plants outcompete the algae for nutrients. This is often suggested by people who I feel don't really get the whole principle behind EI (or similar methods) in that nutrients should be at levels that aren't limiting.

·  Healthy plant growth controls levels of ammonia/ammonium in the water. I've seen two suggestions here; firstly direct competition i.e. the plants remove the NH4/NH3 that the algae need to grow. Alternatively the plants remove the NH4/NH3 thus creating stable conditions in relation to this nutrient with the result that algae are not encourage to enter reproductive phases as they might under less stable conditions.

·  As above but not specifically in relation to NH4/NH3 i.e. generally stable conditions discouraging algae entering reproductive states.

·  Plants produce substances that limit algae growth (allelopathy).

·  Plants are growing fast and the process of pruning, replanting etc. takes place at a rate that is physically faster than that of algae growth.

I'd be really interested to hear peoples thoughts and knowledge of any evidence (including from outside of the aquarium hobby) that points to any particular mechanisms that may be responsible.

Thanks

Neil


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## Jose (13 Mar 2015)

Its probably a few things going on and possibly scientists dont know for sure. Alga seem to sense the plants health condition. If plants arent well then algae blooms. Simple as that. Although there is probably more to it.


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## Another Phil (13 Mar 2015)

Hi Neil,
My thoughts; not knowledge, (just to muddy the waters - ha!);
 is that algal blooms occur in oceans where a lot of  the above doesn't apply, and last year on Woodbury Common a lot of trees were felled and 3 rivulets were flowing out of a bank, 2 were crystal clear and the other was completely green with algae, and there was only about 10ft/3m between them; no other discernible difference which is why I remember it.

The only time I've had more than a bit of green spot on the front glass from sunlight is when I've had a T5 3-4in from the surface and that grew lots of slimy green stuff on the top of everything.
So I can say that with only a single T8 14 inches from the surface, softish water and no CO2 injection I don't get algae with:
 UG air filter, fish and no plants,
Reverse flow UG w ext filter, fish and slowly dying plants,
RFUG with fish, Java moss, java fern, Hydrocotyle and no ferts,
above with a couple of dead fish after holiday heater failure
above minus fish.

Currently Arcadia Stretch LED 18in above surface ( low, low light) over dirted tank with crypts, anubias, java fern and struggling java moss, prob over fertilising as get a bit of white crystal build-up on emergent anubias leaves, and growth is slow but healthy, a first for me. no livestock.
I guess I had ammonia spikes as I didn't mineralise the soil and some plants melted, some died, but no algae.
I'd actually like a light dusting of GSA to give that "lived-in" feel. (I like daisies in lawns, others prefer stripes)

I think algae are opportunists and as such rely on a complex interaction of increases/decreases in their environment to trigger growth, and there is therefore no easy answer,
Sorry, rambling thoughts, not knowledge.
cheers phil


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## herezor (11 Dec 2015)

From my point of view it is simple.

If plants grow healthy, there is less decaying matter as they do not rot. Decaying matter is decomposed by heterotrophic bacteria to different products but the most relevant here is ammonia. Ammonia spikes are one of the main factors for algae blooms (light is also key). 

So if the plants in your tank are healthy, they do release carbohydrates, protein or oils (cell contents and building blocks) at a fixed rate and in low ammounts. These are  broken into pieces at a constant rate (low ammount), NH3 is released at a constant rate (low ammount), and nitrifying bacteria do not have to increase their population (which they do very slowly, much slower than algae) to account for NH3 spikes (which do not occur). Algae do not have an NH3 spike to thrive. So no algae.

Cheers

Pedro


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## dw1305 (11 Dec 2015)

Hi all,





Another Phil said:


> I like daisies in lawns, others prefer stripes


I'm a daisies man as well.

cheers Darrel


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## AndyMcD (12 Dec 2015)

Not quite answering the question, but I think photorespiration may be important. If a plant receives lots of light, but not enough CO2 (or too much O2), the photosynthesis reaction can use O2 instead of CO2. Each time this happens, the reaction produces NH3 and CO2, which the plant re-absorbs, but uses up its stores of energy in doing this. When this happens, the plant needs to absorb less NH3 and CO2 from the water column, meaning more available for the algae. In producing less energy from CO2 and using up more energy to recycle the products, the plant becomes weaker over time.

Another point is biofilm, which builds gradually on all surfaces over time. The number and range of organisms that exist in the biofilm increase over time also. Fast growing plants with quickly expanding leaves that are pruned frequently may not allow the same opportunities for biofilms to mature.


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## AndyMcD (12 Dec 2015)

Jose said:


> Its probably a few things going on and possibly scientists dont know for sure. Alga seem to sense the plants health condition. If plants arent well then algae blooms. Simple as that. Although there is probably more to it.



I think this is very true and I've tried really hard to search for scientific papers concerning what happens to aquatic plants when they become unhealthy, but I run into dead ends. 

Autumn leaves and crypt melt are extreme examples of plants reacting to a change in the environment by shedding compounds.

Lots of studies on how dead Autumn leaves release nutrients, how terrestrial plants react to water stress, how plants recycle by products they may produce if a wrong reaction occurs.

I'm really interested to know what compounds aquatic plants release into the water column, particularly if they become unhealthy. Do they try to optimise themselves to a poorer environment by shedding some of their compounds? If so, I wonder if algae benefits from this, directly or indirectly.

The flip side of this is that healthy plants are absorbing everything from the water column, but if they become unhealthy they stop. I've seen mention of luxury uptake in aquatic plants, where they absorb more of certain nutrients than they need. Perhaps these stores are released when the plant becomes unhealthy.

EI may help to protect against this by ensuring that the environment always exceeds the plant's needs. By ensuring that the plant is healthy, algae isn't given the opportunity to flourish. 

If EI means that there is always an excess of nutrients, why doesn't the algae make use of this excess at all times? 

Poor health of plants may be a more important trigger than an excess of nutrients, but I can't find evidence to support this.


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## PARAGUAY (13 Dec 2015)

Algae one of the earliest forms of life. As we know it its a survivor,in a normal aquatic enviroment its normal for algae to be there and in the aquarium even healthy aquariums its not far away,we limit this as much as we can with repressing it by out competing it with fast growing plants thereby depriving it of taking advantage giving slow growers and mosses time to establish, but to keep all this in balance the trick is cleaning the substrate regular,CO2 accessed all areas,lighting low to start with with shorter as opposed to longer periods, and substrate and fertilisers.Our trick is this balancing act its not easy and we may need help,clean up crews shrimp,tiny algae eating catfish etc I think Tom Barrs EI method is more fertilisers rather than less can be lowered later.The luxury uptake you mention Andy maybe the plants are taking this as needed and healthy plants are out competing algae.Some fertilisers are chelated so maybe thats why so many experts prefer daily dosing so its always available for the plants.Much to be discovered on different plant uptake but one thing we all know deprive fast growers of fertiliser when in full flow and algae is waiting in the wings.


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## roadmaster (14 Dec 2015)

I do not believe plant's can out compete algae for algae need's same thing's plant's need and way less % of these thing's.NO?


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## BruceF (14 Dec 2015)

I would just like to point out that I think this whole concept of non-limiting is a bit problematic.  No one is really endorsing using unlimited amounts of fertilizers in an aquarium.  In fact it might be argued that the prescribed dosing of EI is fairly modest and includes a large water change that helps control the buildup of nutrients in the longer term.


Modern high tech grow systems on the other hand often employ high light 24/7 and hydroponic fertilization that is much closer to what one might call non-limiting. I don’t think anyone is suggesting you can even approximate that kind of regime in an aquarium.


Controlling algae is not simply a function of balancing the dosage of the fertilization but involves limiting the amount of light, maintaining a good supply of oxygen and doing very routine water changes and cleaning etc.  Focusing on the fertilization as the only cause of algae is extremely myopic. My guess would be that it is almost never the cause of the problem. 

(or something like that)


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## hard determinist (14 Dec 2015)

AndyMcD said:


> I'm really interested to know what compounds aquatic plants release into the water column, particularly if they become unhealthy. Do they try to optimise themselves to a poorer environment by shedding some of their compounds? If so, I wonder if algae benefits from this, directly or indirectly. The flip side of this is that healthy plants are absorbing everything from the water column, but if they become unhealthy they stop. I've seen mention of luxury uptake in aquatic plants, where they absorb more of certain nutrients than they need. Perhaps these stores are released when the plant becomes unhealthy.


I'll speculate here, but I think that aquatic plants grow normally, unless they are deprived of some essential nutrients (ignoring the toxicity issues right now). If the deficiency is mild, they begin to sacrifice their older leaves, trying to realocate the missing nutrients into the growing tips (many terrestrial plants do this also). If the deficiency is serious the plants become to die (disintegrate the tissue). So I think that if only the older leaves are rotting, it's not that serious, and there should be no serious algae issue with it. It's just normal process of senescence. According to my experience with algae growth, I think that the algae (or at least some of them) need some time and surface to attach, establish and probably to make some "invasion army" (maybe different generation of the same algae species) which is better suited to colonize the environment. But before the algae change into this better-suited form, it needs time and no disturbance. But that's the main problem in a tank where we do regular water changes, cleaning, and have many algae-eaters there. I noticed in my test tanks, that after some time (usually one week) I begin to see some algae on glass and plants. When I do a water change, clean the tank, but don't clean the plants (and not using any algae eater), the colonization of glass is much faster the second week. Then in some point the algae begin to grow like mad, and in a couple of days I have it just everywhere and the growth rate is just amazing! But if I put some shrimps there (or clean not only the tank but the leaves also), the process of colonization is hindered, and the algae seem to have hard time to take hold of the whole tank. So I believe that it's that simple. No need to speculate on "algae sensing their opportunity" or "NH4 spikes" or similar things. The algae need time & peace. If you give it to them, they'll grow and finally infest the tank even under medium light and/or lower nutrient levels. The nutrient levels don't need to be any high.


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## ceg4048 (14 Dec 2015)

neil1973 said:


> The question: How does EI, or any other method where the aim is to keep all nutrients at levels that are not limiting, help control algae growth?
> 
> I have used such approaches with good results as have many others. I think most would agree that the basic principle is that all nutrients (including CO2) are provided at levels that are sufficiently high as not to limit growth. In such a situation light will become the limiting factor in terms of photosynthesis and plant growth. The result of such an environment is that plants grow quickly and are strong and healthy. It is generally accepted that where there is a sufficient quantity of plants that are healthy and are growing well then algae growth is limited. I have seen this as have many others. What I am interested in is why does this happen?


Hello,
The guiding principle is that algal blooms have become, in a way, a natural mechanism of cleaning up a fouled aquatic system. Of course this isn't the case unilaterally but applies generally. Algae live predominantly as spores, which can bloom into a vegetative state for the purpose of producing more spores. In this way they achieve a sort of immortality because the spores live for hundreds or thousands of years, can be borne on the wind and travel anywhere. Where they land may or may not be suitable for vegetables, so they wait patiently until conditions are right for _their_ vegetables to grow.

As someone else mentioned, there is a huge amount that we do not yet know, but we do know that the spores have the ability to sense the environment and the changes in the environment. The information they sense include thermal properties of the medium, light, as well as a variety of chemicals and the rate of change of the concentration levels of the chemical. Some chemical changes have the effect of being stimulants which encourage the spores to bloom.

Polluted systems typically have a high positive rate of change of a variety of chemicals such as Ammonia. Other chemicals such as Oxygen may have a negative rate of change. Aquatic plants constantly leech all sorts of chemicals into the water column at specific rates. Healthy plants will have some rate and unhealthy plants will have another. Healthy leaves protect their surface from attacks by producing a thin cuticle across the surface. In an unhealthy leaf the cuticle breaks down allowing access to the tissue structure. Growing surfaces also tend to reject anchoring by algae.

Algal spores are sitting on the leaf, so by way of their ability to sample the environment they can tell immediately if a leaf is unhealthy.

There is a laundry list of things that can result in an unhealthy plant, but in the past, one of the biggest culprits, by far has been malnutrition, which prevents the plant from shoring up it's defenses against attacks. The development of EI has always been to eliminate this main avenue of unhealthiness.

As time goes on people lose track of the historical perspective and the significant impact of the development of PMDD/EI in a world where everyone feared that NO3 and PO4 in the water supply were the rogue chemicals that stimulated algal blooms.

At the end of the day you can still have unhealthiness in plants due to other factors, but the purpose EI and other systems such as ADA and so forth are to ensure that malnutrition is not one of those factors.



neil1973 said:


> · The healthy plants outcompete the algae for nutrients. This is often suggested by people who I feel don't really get the whole principle behind EI (or similar methods) in that nutrients should be at levels that aren't limiting.


Algae can thrive in nutrient poor waters thousands of times less concentrated that any plant could ever hope to. There is no chance for any plant to ever out-compete algae.



neil1973 said:


> · Healthy plant growth controls levels of ammonia/ammonium in the water. I've seen two suggestions here; firstly direct competition i.e. the plants remove the NH4/NH3 that the algae need to grow. Alternatively the plants remove the NH4/NH3 thus creating stable conditions in relation to this nutrient with the result that algae are not encourage to enter reproductive phases as they might under less stable conditions.


Again, NH3 is only one of the many chemicals, whose loading rate in the water column algae can use to determine suitability for blooming. Algae sitting on a decaying leaf will see all kinds of chemicals bleeding into the water column.



neil1973 said:


> · As above but not specifically in relation to NH4/NH3 i.e. generally stable conditions discouraging algae entering reproductive states.


Yes, this is true generally. Plants do best in stable and comfortable environment where algae welcome instability. Instability is a sure sign of a decaying environment.



neil1973 said:


> · Plants produce substances that limit algae growth (allelopathy).


Algae rule plants. There is no data demonstrating allelopathy.



neil1973 said:


> · Plants are growing fast and the process of pruning, replanting etc. takes place at a rate that is physically faster than that of algae growth.


Although growth rate is one of the factors that limit a plants liability, it is not the only factor as discussed above.

Cheers,


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## alto (14 Dec 2015)

ceg4048 said:


> There is no data demonstrating allelopathy.


these published papers are then all smokescreens 
-  the authors scammed not just the journal publication teams but there is a world wide conspiracy involved in the coverup - as all papers would've been peer reviewed ...

Or you proscribe to the belief that aquarium plants are "special stars" that won't follow general plant behaviour 



From the University of Florida IFAS Extension
EDIS

*Allelopathy:How Plants Suppress Other Plants*
James J. Ferguson, Bala Rathinasabapathi, and Carlene A. Chase


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Then there is also the entire field of Natural Product Chemistry


Published texts such as

*Comprehensive Natural Products Chemistry*

or a huge selection of scientific published papers

Natural products – learning chemistry from plants.
Staniek A, Bouwmeester H, Fraser PD, Kayser O, Martens S, Tissier A, van der Krol S, Wessjohann L, Warzecha H.
*Abstract*
_Plant natural products (PNPs) are unique in that they represent a vast array of different structural features, ranging from relatively simple molecules to very complex ones. Given the fact that many plant secondary metabolites exhibit profound biological activity, they are frequently used as fragrances and flavors, medicines, as well as industrial chemicals. As the intricate structures of PNPs often cannot be mimicked by chemical synthesis, the original plant providers constitute the sole source for their industrial, large-scale production. However, sufficient supply is not guaranteed for all molecules of interest, making the development of alternative production systems a priority. Modern techniques, such as genome mining and thorough biochemical analysis, have helped us gain preliminary understanding of the enzymatic formation of the valuable ingredients in planta. Herein, we review recent advances in the application of biocatalytical processes, facilitating generation of complex PNPs through utilization of plant-derived specific enzymes and combinatorial biochemistry. We further evaluate the options of employing heterologous organisms harboring PNP biosynthetic pathways for the production of secondary metabolites of interest._

- not to mention the pharmaceutical industry centred around natural plant chemistry ....

That plants may produce natural chemistry products that may affect algae is not some "_far reach_" supposition.

Apolgies for the off-topic post


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## ceg4048 (17 Dec 2015)

alto said:


> That plants may produce natural chemistry products that may affect algae is not some "_far reach_" supposition.



Have you demonstrated it in your tank? I'm not impressed by any of your references. Wheat and the other mentioned agricultural crops do not grow underwater. All of those references are data applicable terrestrial plants.

There are lots of plants and trees that produce natural insecticides, for example. A lot of our medicines come from plants in their war against each other and against browsers. In aquatic plants however, there has not been any data to show the ability of any aquatic plant to poison algae or to poison other plants. If you believe this then you are dreaming, because it's very easy in a healthy tank to induce any of the common tank algal species. All you have to do is to withdraw specific nutrients or perturb flow/distribution or use unreasonable light levels without compensation. No alleopathic chemical produced by your cabomba can ever suppress algae.

Algae are the predators and plants are the prey. It's a much better mindset to approach plant health in this way than to advocate dreamy personal visions of chemical warfare. The battles in our tanks occur in a very different way and on a very different level.

In The Matrix it's a very popular pastime to extrapolate data from terrestrial and automatically apply it to aquatics, then to program an entire population to believe that apple trees have the same dynamic as submerged Hygrophilla.

Water changes everything...

Cheers,


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## Jose (23 Dec 2015)

I've got one thing bugging me for some time now. Do typical true aquatic plants like egeria, vallisneria etc leach as many chemicals into the water as other more high tech plants like hc or althernantera? The reason I ask is because in a fast growing tank with co2 and harder plants it seems like algae is inevitable after some time as a result of organic buildup, unless you keep doing nice big water changes. Is a high tech tank actually a healthy ecosystem at all for the critters, I think only with lots of WCs. We definately dont have a stable ecosystem, at least not stable on its own. If we kept only vallis, egeria, miriophylum, and lower tech plants, would it be easier to maintain a chemically perfect environment? Or do they still foul the water anyway?


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## PARAGUAY (23 Dec 2015)

This is a good question. I think it comes down to the way these plants grow -fast/faster if conditions ie nutrients,light,water changes and tank cleanliness are good,then they become good oxygenators spreading to minimise algae problems.The advantage then is slow growers or more difficult ones can establish in ideal conditions ,the question of leaching waste at what rate?is not important. For the benefit of oxygen and conditions they are then providing helps photosynthesis and plant growth and as you mention WC then  dilute and remove waste. Its a well known way of clearing algae in a pond throwing in a few bunches of Canadian Pond Weed.Not much science here just the way I see it?


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## Jose (23 Dec 2015)

PARAGUAY said:


> This is a good question. I think it comes down to the way these plants grow -fast/faster if conditions ie nutrients,light,water changes and tank cleanliness are good,then they become good oxygenators spreading to minimise algae problems.The advantage then is slow growers or more difficult ones can establish in ideal conditions ,the question of leaching waste at what rate?is not important. For the benefit of oxygen and conditions they are then providing helps photosynthesis and plant growth and as you mention WC then dilute and remove waste. Its a well known way of clearing algae in a pond throwing in a few bunches of Canadian Pond Weed.Not much science here just the way I see it?



But, it can be quite important. Specially if the aim is to maintain the healthiest tank possible e.g if you're keeping Discus at the same time as reducing water changes. Sorry for digressing. We all want to work less don't we. For example: If you only keep a tank with lemna minor  you probably don't need water changes if bioload is low enough, which means that the plant is not adding organics into the water, like an iwagumi tank would be. They are both growing at a very fast pace and they can both be under very high light. But stability is very different in both.


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## PARAGUAY (24 Dec 2015)

@Jose. your quite right it is important I think there is a lot to be discovered yet -why certain plants take more of a certain nutrient than others, how some plants thrive with little or no nutrients.Different water parameters effecting plants differently.Given the wrong conditions many plants just die some plod on in a limited capacity?


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## roadmaster (5 Jan 2016)

Spring and summer month's ,I spend a considerable amount of time waste deep in pond's and lakes casting artificial lures among the lilly pad's and other aquatic vegetation or weed's for largemouth bass .
Have often noted that while wading and casting my lure's that a group of lilly pad's,or other invasive weed's to my right, may be healthy green and flowering, while those just a few feet away to my left may be brown and or in poor health.
Have also noted that the aquatic weed's on the west side of the lake or pond are often the ones that seem to flower, or mature sooner than those on the east side of the lake or pond.
Maybe the plant's on the west side catch the light sooner of a morning ,and receive a bit more light throughout the day than the plant's on the east side  I do not know.
I believe that some plant's are just better at gathering what they need for good growth than other's.
Do recall an article from  The botanical review, July-Sept 1993  entitled.. "Competition and Alleopathy in aquatic communities"  for those who might like to search it out.


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## alto (8 Feb 2016)

ceg4048 said:


> In aquatic plants however, there has not been any data to show the ability of any aquatic plant to poison algae or to poison other plants.


Someone brought this old topic back to mind so again not sure what exempts these sorts of studies  ... quite certain that _M spicatum_ would qualify as an "aquatic plant" by most definitions 

I'd also consider these to fit the criteria of "aquatic plant"
_Elodea nuttallii
Elodea Canadensis
Stratiotes aloides
Myriophyllum verticillatum
_


_*Myriophyllum spicatum-released allelopathic polyphenols inhibiting growth of blue-green algae Microcystis aeruginosa*
Satoshi Nakai,  (M), Yutaka Inoue, Masaaki Hosomi, Akihiko Murakami (M)

*Abstract*



			A culture solution of macrophyte Myriophyllum spicatum was subjected to algal assay-directed fractionation on the basis of polarity and molecular weight. As the water-soluble fraction below molecular weight 1000 was the only fraction to inhibit the growth of blue-green algae Microcystis aeruginosa, it was analyzed by analytical high-performance liquid chromatography (HPLC) and atmospheric pressure chemical ionization mass spectrometry (APCI-MS) in order to identify M. spicatum-released growth-inhibiting allelochemicals. Both HPLC and APCI-MS revealed the release of four polyphenols exhibiting growth inhibition effects, i.e., ellagic, gallic and pyrogallic acids and (+)-catechin. A quantitative investigation of their respective inhibitory effects showed that (1) gallic and pyrogallic acids are more inhibitory than (+)-catechin and ellagic acid, and that the autoxidized products of each polyphenol demonstrated growth inhibition. Finally, when the collective activity of a mixture of the polyphenols was examined, synergistic growth inhibition of M. aeruginosa occurred.
		
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*Study on the mechanism of allelopathic influence on cyanobacteria and chlorophytes by submerged macrophyte (Myriophyllum spicatum) and its secretion*
Junying Zhua,, Biyun Liua, Jing Wanga,, Yunni Gaoa, Zhenbin Wua,

*Abstract*



			For revealing the mechanism of allelopathic influence on phytoplankton by aquatic macrophytes, the growth and photosynthetic activities of cyanobacteria Microcystis aeruginosa and the chlorophyte Selenastrum capricornutum were investigated when they coexisted with submerged macrophyte Myriophyllum spicatum and were exposed to allelopathic polyphenols: pyrogallic acid (PA), gallic acid (GA), ellagic acid (EA) and (+)-catechin (CA). According to the results of coexistence assays, the non-photochemical quenching (NPQ) and effective quantum efficiency (YII) of M. aeruginosa were affected earlier and more rapidly than the cell density. However, the influence of M. spicatum on S. capricornutum was not found. When the Toxicity Index (TI) was applied to evaluate the combined effects of binary and multiple mixtures of polyphenols, it was found that the four tested polyphenols with the proportion identified in the M. spicatum-cultured solution were observed to present synergistic effect (0.36–0.49) according to the cell density, NPQ and YII of M. aeruginosa. With the combined effects of polyphenols on S. capricornutum, only additive action (0.52–1.62) was found. On the other hand, PA (2.97 mg L−1), GA (2.65 mg L−1) caused significant reductions of photosystem II (PSII) and whole electron transport chain activities of M. aeruginosa by 71.43 and 18.37%, 70.95 and 40.77% (P < 0.05), respectively, after 24-h exposure, but no inhibition effect was found in S. capricornutum. The dark respiration and photosystem I (PSI) activities of M. aeruginosa were significantly increased by exposure to PA and GA (P < 0.05). Nevertheless, EA and CA had no influence on the electron transport activities of the tested organisms. These results indicate that the reduction in photosynthetic activity of M. aeruginosa and the synergistic effect of allelochemicals may be two important causes for the inhibition of undesired phytoplankton by submersed macrophytes in natural aquatic ecosystems, and PSII in cyanobacteria is considered to be one of the target sites attacked by allelopathic polyphenols.
		
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ALLELOPATHIC GROWTH INHIBITION OF SELECTED PHYTOPLANKTON SPECIES BY SUBMERGED MACROPHYTES1
Sabine Körner and Andreas Nicklisch

*Abstract*_


> _
> Allelopathic effects of submerged macrophytes on the growth and photosynthesis of different unialgal cultures of planktonic cyanobacteria, a diatom, and a green alga were tested in coexistence experiments using dialysis cultures. The method applied allowed measurements under conditions similar to that in lakes but without nutrient and light limitation. Growth and photosynthesis were measured with a pulse amplitude modulated fluorometer as an increase of chl a fluorescence and activity of PSII, respectively. Eurasian water milfoil Myriophyllum spicatum L. and rigid hornwort Ceratophyllum demersum L. proved to inhibit the PSII activity and then growth of the investigated phytoplankton species, whereas sago pondweed Potamogeton pectinatus L. showed no effect. Growth inhibition was dependent on biomass of M. spicatum. Considerable differences between phytoplankton groups and among species of cyanobacteria were found regarding their response to M. spicatum. Members of the Oscillatoriales and Microcystis aeruginosa Kütz. emend. Elenkin were more sensitive than the cyanobacterium Aphanizomenon flos-aquae Ralfs ex Born. et Flah., the diatom Stephanodiscus minutulus (Kütz) Cleve et Möller, and the green alga Scenedesmus armatus Chodat. A possible contribution of this result to changes in the phytoplankton succession of lakes after loss of macrophytes is discussed._





The authors of this article are less retiring in their statements - this article is open access & includes reference links

*Interactions between invasive Eurasian watermilfoil and native water stargrass in Cayuga Lake, NY, USA *
_Bin Zhu,and Samuel E. Georgian_


> _
> Allelopathy as a non-resource interaction between plants plays an important role in shaping plant communities (Gross 2003; Yuan et al. 2013). Allelopathic effects among aquatic plants have been well documented (see reviews by Gopal and Goel 1993; Gross 2003). Allelopathy occurs in all aquatic habitats, and all primary producers are capable of producing and releasing allelochemicals—‘novel weapons’ to provide a competitive advantage (Callaway and Ridenour 2004; Gross 2003; Svensson et al. 2013). Allelochemicals have been shown to help invasive aquatic plants and algae outcompete natives. For example Eurasian watermilfoil extract contains hydrolysable polyphenols and inhibits the growth of cyanobacteria, green algae, duckweed and epiphytes (Elakovich 1989; Elakovich and Wooten 1989; Planas et al. 1981). The non-native macroalga Bonnemaisonia hamifera was reported to inhibit the settlement of native macroalgal propagules and microalgae through allelopathy in Scandinavian lakes (Svensson et al. 2013). Native plants have also been shown to release allelochemicals to inhibit the growth of other primary producers including invasive plants (Gross 2003). Elakovich (1989) investigated 16 aquatic plants and found that Nymphaea odorata and Brasenia schreberi had strong allelopathic effects on the growth of duckweed Lemna minor. Allelochemicals from aqueous extracts of Eleocharis species including E. coloradoensis, E. interstincta and E. cellulose were found to retard the growth of invasive Hydrilla verticillata (Ashton et al. 1985; Sutton and Portier 1991). Similar studies have indicated that many native plants including eelgrass, coontail (Ceratophyllum demersum) and American lotus (Nelumba lutea) had allelopathic effects on Eurasian watermilfoil (Gross 2003; Jones 1993; Vance and Francko 1997)._


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## sWozzAres (8 Feb 2016)

neil1973 said:


> ·  Plants produce substances that limit algae growth (allelopathy).



Actually the opposite is true, plants are known to produce hormones that stimulate spore germination in some algae.

_Plant hormones such as indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), naphthalene-2-acetic acid (NAA), gibberellic acid (GA3), kinetin, and tryptophan (a precusor of IAA) at certain levels (either individually or in combination) stimulated SG in some algae (Table IV; p. 288). They probably promote cell enlargement, cell division or have some other cellular and molecular effects._

*Factors affecting spore germination in algae — review*
http://link.springer.com/article/10.1007/s12223-009-0047-0


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## alto (8 Feb 2016)

Unfortunately I cant read this review (no open access) & can't seem to find the magic word series for Google to list related articles in the first few result pages 
- are these substances actually released into the surrounding aquatic environment? or is this a series of extracted compounds applied to the algal spores & effects observed?

Just to get this slightly on topic 


> providing unlimited nutrients helps control algae?


in some of the papers I linked, reduced levels of phosphate & (nitrates?  guilty of skimming  ) were also observed in the "algae-free zone" surrounding the plant mass, & this nutrient "deprivation" was considered a factor in algal limitation  

(or perhaps this detail was included in some of the papers I neglected to link   - there are many, many examples of allelopathy, published in various journals, authored in many countries ...
ie not some research group's pet project)


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## 691175002 (8 Feb 2016)

I think the main evidence that allelopathy is not dominant in aquariums is that if plants were secreting chemicals that inhibited algae, performing a water change should dilute these chemicals and immediately result in an algae bloom.

I'm sure that healthy plants are able to defend themselves against algae, but tying it to a specific mechanism is hard because there are so many contradictory examples.

If you consider algae as a population that goes through booms and busts; keeping it suppressed by reducing areas for it to reproduce (healthy plants), limiting its main source of food (ammonia? organics?), and culling whenever possible (cleanup crew, manual removal), should ensure that algae cannot get a foothold in the tank.

This seems pretty consistent with my experience.


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## alto (8 Feb 2016)

691175002 said:


> I think the main evidence that allelopathy is not dominant in aquariums is that if plants were secreting chemicals that inhibited algae, performing a water change should dilute these chemicals and immediately result in an algae bloom.


You're expecting grand gestures from a microscopic (picoscopic?) process


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## Soilwork (11 Feb 2016)

Is it really a question of plants defending themselves, algae invading, lying in wait, waiting to attack, scavenging, looking for weakness etc etc. Yes the goal of organisms is to survive but why? Is there a bigger picture? Plants and algae have the same purpose no? To support life on Earth.  Whatever the mechanism is that induces/suppresses algae perhaps they are working together to support an ecosystem?  If algae can live as spores for such a long time then why not allow higher plants to carry the torch?  Plants carry food, provide shelter, spawning sites, materials and provide massive amounts of oxygen.  If the plants can no longer do this then the ecosystem is in peril.  Plants are decaying and sending out signals to the algae.  The algae mearly begin to take over the role of supporting the ecosystem.  They use  food the plant releases to Gain a foothold. They use leaves for this and to get closer to the light.  The plants are dying fast and the algae need to spread quickly to keep the system alive. Algae take over.  Then when the conditions become right again for plants they grow once more, the ecosystem is safe and algae resides back in wait just in case they are called in to action again.

This is how I like to look at it.  It stops me from swearing when I'm scraping the GSA off the back of my tank.


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## AndyMcD (1 Mar 2016)

Here's my latest brainstormed theory, based upon what I've read, but also some of the points ceg4048 has made have struck a chord with me:



ceg4048 said:


> spores have the ability to sense the environment and the changes in the environment. The information they sense include thermal properties of the medium, light, as well as a variety of chemicals and the rate of change of the concentration levels of the chemical. Some chemical changes have the effect of being stimulants which encourage the spores to bloom.





ceg4048 said:


> Polluted systems typically have a high positive rate of change of a variety of chemicals such as Ammonia. Other chemicals such as Oxygen may have a negative rate of change.



I think algae spores are waiting for an increasing rate of change in ammonia (not necessarily a high concentration, a spike may be sufficient). When they sense this, they germinate and begin a rapid growth phase.

Ammonia is important to algae for a number of reasons:
- with a higher proportion of protein than plants, a source of nitrogen in a useable form is very important for growth
- it indicates that something in the environment is decaying, possibly meaning less competition from plants
- it means that there is an increasing population of heterotrophic bacteria breaking down proteins to amino acids and hence ammonia. With a large decaying food source the population of bacteria may flourish. The heterotrophic may be out competing the autotrophic bacteria as less ammonia is being converted to nitrates.

Unhealthy plants mean decay, releasing an increased amount of ammonia into the environment.

Effects such as photorespiration (too much light for too little CO2) means the plant may be absorbing less ammonia, acting to increase the ammonia concentration.

However, I also think the algae is then waiting for a reduction in the oxygen concentration, which indicates:
- it is time to stop growing and to produce spores to create the next generation
- photosynthesising plants are producing less oxygen. There is less plant mass and the bacteria's food source may be reducing. The amount of ammonia being released is going to reduce
- the heterotrophic bacteria population is reaching a peak and is consuming much of the available oxygen. The bacteria may be producing the vitamins the auxotrophic algae needs to reproduce

Healthy plants absorb ammonia, are not a source of ammonia and produce oxygen.


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## sWozzAres (2 Mar 2016)

Presence of ammonia/ammonium and anoxic conditions (lack of oxygen) is known to reduce spore germination, not increase it.

Pollutants, such as heavy metals (Hg, Cu, Cr, Co, Zn, Pb, etc.), pesticides or insecticides (carbofuran, 2,4-D, dithane, phorate, bavistin, parathion, etc.), sewage effluent, crude oil, acetylene, ethylene, ammonium, etc. at various levels decreased spore liberation, motility, settlement, and GRM in different algae (Table X; p. 291). 

Biotic factors (including algal and bacterial extracellular products, animal grazing and extracellular products), water stress (except for the need of prior drying for some algal spores), antibiotics (except penicillin at some low level), UV light, and pollution (including heavy metals, pesticides, insecticides, sewage effluents, crude oil, acetylene, ethylene, ammonia or anoxic conditions) at various levels decreased or totally suppressed SG.

Factors affecting spore germination in algae — review
http://link.springer.com/article/10.1007/s12223-009-0047-0


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## BigTom (2 Mar 2016)

^ Pretty thorough paper that. I've got a pdf if anyone wants it (pm with an email address).

Interesting excerpt (SG = spore germination) -



> The SG was decreased not only by the lack of nitrogen, phosphorus or magnesium but also when their (and of calcium) concentration exceed certain levels; e.g., nitrate or phosphate at ≥5-fold level, or magnesium at 10-fold level of that present in the basal medium inhibited akinete GRM in Westiellopsis prolifica (Agrawal and Sharma 1994a). Magnesium at ≥5-fold level or calcium at ≥2-fold level also inhibited akinete GRM in Stigeoclonium pascheri (Agrawal and Sarma 1982a). This indicates that SG in algae is sensitive to high levels of inorganic nutrients. Omission of microelements (ZnSO4, MnCl2, MoO3, CuSO4, Co(NO3)2, H3BO3) from the basal medium increased SG in Stigeoclonium pascheri, and by increasing their concentration to ≥2-fold levels, the condition was reversed (Agrawal and Sarma 1982a). The presence of microelements in the basal medium therefore serves as a check in reaching maximum level of SG under control conditions. More study is needed to clear the role of micro- and macronutrients in SG.


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