Why is bigger plant mass better ?

[Deano3]

Just a quick question many people say bigger plant mass the better is it because they use all nutrients and oxygenate the water ?



Thanks Dean

 

[Lindy]

I think you just answered your own question

 

[Claire]

As far as I understand, it means that there is less chance of algae getting a good hold initially as the plants will be using lots of nutrients. Even though excess nutrients do not cause algae, they will fuel the fire. Basically it gives you a bit of a safety net for any early imbalances/mistakes.

 

[jose_j]

It is widely known that plants compete with algae for resources, so as the plant mass increases algae find less growing opportunities. But I think that a key point is alellopathy, that is, inhibition of algae growth due to specific plant-produced allelochemicals (e.g., phenolic compounds, sulfur-containing compounds, oxygenated fatty acids, etc.). There are many scientific publication regarding this issue, like for example:

An examination of the phytotoxicity of the water shield,Brasenia schreberi - Springer
Allelopathic growth inhibition and colony formation of the green alga Scenedesmus obliquus by the aquatic macrophyte Stratiotes aloides - Springer
Growth inhibition of blue–green algae by allelopathic effects of macrophytes
ALLELOPATHIC EFFECTS OF SEVERAL AQUATIC PLANTS ON ALGAE--《Acta Hydrobiologica Sinica》1992年01期


If this is true, a densely planted tank with a high species diversity is more likely to be protected against algae blooms. But of course this is just my opinion.

Hope this message will help you.

Cheers,

Jose

 

[Michael W]

I don't think there is any conclusive solid data about Allelopathy. Having a large plant mass does not necessarily reduce algae if the plants are doing poorly. Plants in poor conditions will promote algae that will grow on them like if a person is unhealthy then he is likely to fall ill. There are people out there who keep a single species tank that will little to no visible algae which could be down to good cleaning and good plant health.

Algae can out compete plants in many ways yet in planted tanks with sensible lighting and healthy plants be it growing slow or fast algae problems still rarely occur on the plants themselves, you may still get some on the glass but with good maintenance on your part it may not take hold.

 

[dw1305]

Hi all,
I think that the jury is still out on how important allelopathy is in aquatic plants. This is a good starting point - Gross (2003) "Allelopathy of Aquatic Autotrophs", <http://www.jlakes.org/web/Allelopathy_aquatic-autotrophs-CRPS2003.pdf>, she still works at the University of Konstanz <KOPS - Institutional Repository der Universität Konstanz>, and a lot more papers are available from them (search for "Elisabeth Gross").

Ceratophyllum definitely reduces the growth of both Cyanobacteria and filamentous greens, but how much of that is down to its allelopathic exudates still isn't clear. My suspicion would be that it always has more to do with competition for resources than allelopathy, but that is only a guess.

However there definitely is something about a large plant mass that makes tank management easier. Have a look at this thread. <Low tech questions? | UK Aquatic Plant Society>.

cheers Darrel

 

[kirk]

I think the jury may just be out on that one I think the jury may just be out on that one

 

[jose_j]

I don't think there is any conclusive solid data about Allelopathy. Having a large plant mass does not necessarily reduce algae if the plants are doing poorly. Plants in poor conditions will promote algae that will grow on them like if a person is unhealthy then he is likely to fall ill. There are people out there who keep a single species tank that will little to no visible algae which could be down to good cleaning and good plant health.

Algae can out compete plants in many ways yet in planted tanks with sensible lighting and healthy plants be it growing slow or fast algae problems still rarely occur on the plants themselves, you may still get some on the glass but with good maintenance on your part it may not take hold.

Hi Michael,

i found you comments very interesting. Available evidence tells us that there is conclusive solid data about Allelopathy, just search for high impact factor research papers in Scholar Google using the words "allelopathy" "aquatic" "plants" "algae". You had a point when talking about plant health, of course this is really important. So regarding the question that entitles this thread: Why is bigger plant mass better? I would answer that its a matter of ecological competition for resources including space. (Healthy) plants compete with algae for nutrients, light, CO2, etc and they also compete biochemically releasing compounds that inhibit the growth of algae (and other plants as well!). Of course I'm not saying that if you don't have a big plant mass your tank will be an algae crop, but doing so it should be less likely. As an example I can give you my current tank, that holds 27 plant species all of them in good shape in terms of health, and where I have never seen a single algae (yet):

300L pseudo-Dutch style Planted Tank | UK Aquatic Plant Society

In summary, plants compete with algae "eating" the available resources (nutrients, light, etc) and they also fight against other species (algae, other plant species, bacteria, etc) releasing chemicals compounds that can inhibit growth or cause death.

 

[NatureBoy]

I'm convinced that allelopathy plays a role in our aquariums, however nutrient competition goes hand in hand so is difficult to figure. I'm pretty sure I've seen it with eleocharis and glossostigma, where the glosso literally upped camp and left the substrate as soon as an eleocharis runner came close, but then someone will have a tank with these two growing intertwined no probs...

Why does algae not gain a foothold on a healthy leaf? Is is because the healthy leaves have the energy they need to produce the chemicals that prevent algae gaining a foothold? not sure...

 

[Michael W]

i found you comments very interesting. Available evidence tells us that there is conclusive solid data about Allelopathy

Hi Jose,

I acknowledge Allelopathy, what I meant was soild conclusion on how effective it really is at controlling algae which is still questioned as pointed out by Darrel.

 

[jose_j]

Hi Jose,

I acknowledge Allelopathy, what I meant was soild conclusion on how effective it really is at controlling algae which is still questioned as pointed out by Darrel.

Hi Michael, you are right and I fully agree with you, we don't know how important the role of allelopathy is in our tanks. It would be great to get a device for monitoring allelochemical levels in the tanks, or even better, to get the allelochemicals themselves and dose them in the tanks in order to test their effects on algae.

 

[Deano3]

Well thanks everyone think I have a good idea now, that too many nutrients don't cause algae but once it's gets a foothold it starts competing with the plants for nutrients co2 light space etc so the more plants in tank the more nutrients and co2 they want and not much left for algae but if only couple of plants the algae wants more and more and there is plenty of nutrients not being use so they flourish, better to stock full then thanks so much for time and information everyone




Thanks Dean

 

[ceg4048]

Hello,
At no point are plants ever capable of competing with algae for resources. You'll need to erase that concept from your thinking, otherwise it will lead you into a cul-de-sac when troubleshooting plant health issues.

As for large plant mass, the real reason it is an advantage has more to do with the general effect the plant has on it's environment. Plants do not need to use alleopathy in order to control their environment. They actively change the local environment in order to suit their needs as a matter of course. No special poisons are necessary.

Plants oxygenate the soil as well as the water column, and in so doing, they automatically exclude certain species of pathogens that depend on anerobic conditions to thrive. Plants also excrete simple sugars and other byproducts which feed other microorganisms, and in turn, those microorganism produce products which benefit the plants.

There is a wide, hugely complex series of chemical exchanges involving plants and environment. They suffer because WE are the ones that control the environment, and we do a miserable job of it generally. So instead of blaming poor performance on imaginary chemical warfare, we should instead rely on known environmental factors which directly affect the health of plants. High nutrient loading and ample CO2, combined with frequent and large water changes benefit plants, regardless of their level of mass, however, since more plant mass has a higher impact on the environment, then it is always an advantage to have a higher mass (although higher mass can also have a negative impact in a tank, such as flow/distribution blockage).

Cheers,

 

[Lindy]

Its lovely to have you back Clive.