# Could floating plants be it?



## jlm (28 Jun 2009)

Still on the subject of setting up a new El Natural tank, it strikes me that an abundance of floating plants - duckweek, water lettuce, etc... - may be the soultion to a dead-easy maintenance aquarim setup: given sufficient quantity, to the point of totally covering the water surface of the tank, would they alone provide enough oxigen for a few fish, and would they consume enough nutrients to defeat any algae growth?

Then one could concentrate on rock-scaping the bottom of the tank.

Floating plants enjoy maximum light and co2, require no substratum and generally are quite beneficial to the tank's ecosystem.

I can think of two possible scenarios:

1 - Floating plants alone covering 100% of the water surface, ie no plants of any other sort, with or without substratum.

2 - Dividing the tank in two parts, the first area as in 1 above (only floating plants), the second with the usual set up: substratum and rooted/anchored plants.

I would be interested to know if this setup can work, as an alternative in case things go wrong with the usual planted aquarim.


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## ceg4048 (28 Jun 2009)

Hi,
     Nutrients don't cause algae. Therefore the entire scheme is built on a house of cards. As discussed earlier, the symbiosis between plant and substrate bacteria is broken with floating plants. Besides, what is there to look at in a tank full of floating plants? A bunch of roots and a dim, barren interior? What's the point? Duckweed is a nuisance, so as far as I'm concerned, one may as well have algae. Now of course, one could design an arrangement so that the water level is low and so that surface plants can be viewed more easily. I suppose one is only limited by one's imagination on that score, but this completely misses the point. There are plenty of non-CO2 tanks that are beautifully scaped and are low maintenance.

Again, if you'd prefer to go this way I can only comment from an aesthetic viewpoint and that is only an opinion. If your aesthetic goal is a sort of minimalism with rockwork (like a Japanese rock garden) then that's a different issue, but doing this because you're afraid things might go wrong otherwise is not rational. Scientifically you're not really gaining anything - and the more you worry about nutrients, the more algae you will have. Read this sticky thread in the Algae section=> Good algae article There are fundamental misconceptions about the cause of algae and that's why there is so much algae.

Edit: Regarding the point about combining floating and substrate plants. This is a very effective idea because it will limit the light reaching into the tank. Dusko has done this very effectively as shown in this thread=> Green Water - Dusko's lazy solution to the problem The key is that he has not abandoned the substrate plants and he uses just enough floating plants to limit the light, but not so much that the plants below are starved of light. It's this light that triggers algal blooms.

Cheers,


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## jlm (28 Jun 2009)

ceg4048 said:
			
		

> Hi,
> Nutrients don't cause algae. Therefore the entire scheme is built on a house of cards. As discussed earlier, the symbiosis between plant and substrate bacteria is broken with floating plants. Besides, what is there to look at in a tank full of floating plants? A bunch of roots and a dim, barren interior? What's the point? Duckweed is a nuisance, so as far as I'm concerned, one may as well have algae. Now of course, one could design an arrangement so that the water level is low and so that surface plants can be viewed more easily. I suppose one is only limited by one's imagination on that score, but this completely misses the point. There are plenty of non-CO2 tanks that are beautifully scaped and are low maintenance.
> 
> Again, if you'd prefer to go this way I can only comment from an aesthetic viewpoint and that is only an opinion. If your aesthetic goal is a sort of minimalism with rockwork (like a Japanese rock garden) then that's a different issue, but doing this because you're afraid things might go wrong otherwise is not rational. Scientifically you're not really gaining anything - and the more you worry about nutrients, the more algae you will have. Read this sticky thread in the Algae section=> Good algae article There are fundamental misconceptions about the cause of algae and that's why there is so much algae.
> ...




Hi ceg4048,

Mm, I thought it was quite established that a sufficient quantity of healthy and growing plant-mass is critical in keeping algae at bay, supposedly by dint of simply outcompeting these for nutrients, ie the algae are starved into non-existance, so to speak, by the plant growth. As the article says, â€˜the more we dose the less algae we getâ€™, yes, but because of healthy plant growth, no?

In any case, my point by proposing a floating plant tank isnâ€™t to fight algae per se (this is a secondary issue, at least for the moment   ) but to explore this option by itself and to resort to it in case one fails with plants and is about to throw in the towel - it has been know to happen!

So, again, would it technically be possible to replace all or most of the rooted/anchored plants with floating plants in a El Natural setup, do you think? I am uncertain whether a water surface area more or less totally covered with floating plants can perform a similar biological function as the standard planted setup. What sort of fish / floating plant quantity ratio would be successful, and would this sort of plants welcome fertilizing, perhaps?

Re. the â€˜symbiosis between plant and substrate bacteriaâ€™, is this strictly necessary, having a biological filter in the tank? Not sure about this one, either. 

In the excellent â€˜Good algae articleâ€™ (http://www.aquariumalgae.blogspot.com/) it is stated that â€˜Even though plants can get most of the nutrients via soils we have to bear in mind that soils will become exhausted after approximately 6-12 month. To prevent this from happening it is beneficial to dose macro and micro nutrients via dry or liquid fertilisers once a week.â€™

This quite confuses me: you cannot 'prevent' the soil becoming exhausted, can you? It is going to happen whether you add liquid nutrients or not, surelyâ€¦ I suppose what it means is that once exhausted, the road to follow is to add ferts in one way or another.

Thanks for the links, they are great help, as all your comments


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## Dave Spencer (29 Jun 2009)

jlm said:
			
		

> Mm, I thought it was quite established that a sufficient quantity of healthy and growing plant-mass is critical in keeping algae at bay, supposedly by dint of simply outcompeting these for nutrients, ie the algae are starved into non-existance, so to speak, by the plant growth. As the article says, â€˜the more we dose the less algae we getâ€™, yes, but because of healthy plant growth, no?



Plants do not, and cannot outcompete algae for nutrients. In a nutrient deficient environment, algae can thrive whilst plants will falter. 

Dave.


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## jlm (29 Jun 2009)

Dave Spencer said:
			
		

> jlm said:
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Ok, so just how does a healthy growing plant mass prevent the onset of algae? The more I research about algae, the more confused I get!


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## Brenmuk (29 Jun 2009)

Floating plants provide extra shade and they have the ability to use aerial CO2 so can play an import part in an el natural set up. But what really makes the el naturel style tank is a good rich soil substrate and lots of sunlight.
If you have a soil substrate then you will need plants to root in it because the roots oxygenate the soil and stop it going anaerobic.
If I were to set up a tank without soil I would go for a thin layer of gravel/sand at the bottom - max 1cm and use floating plants and perhaps java fern/anubias tied to rocks and wood. I think maybe it would be more maintenance in the long run because when I have done similar set ups for shell dwelling cichlids in the past the tank has become overrun with detritus after a while and weekly water changes and gravel hoovering were not enough.
A soil substrate seems (ime) to provide a more complete ecosystem and surprisingly far less maintenance.

Ironically because floating plants are not limited in their growth by CO2 they can grow very rapidly and can strip the tank of its nutrients faster than they can be replenished in an el natural tank that is not supplemented by additional ferts. I have had 2 outbreaks of BGA in my tank and both I associate with rampant growth of floating plants causing low nitrate levels (the bga first appeared on the roots of water lettuce). So I am wondering if a tank based on floating plants alone can be a balanced tank.


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## ceg4048 (29 Jun 2009)

Hi,
    As Dave points out, there is no competition between higher plants and algae because they have totally different requirements. So it really doesn't matter what level of nutrients in in the water, low or high. We can see this demonstrated in tanks all over the world. However, yes, it is a good idea to have a sufficient mass of plants. Again, this is the problem with interpretation of the facts. No mass of plants can possibly compete with algae. This is not what plant mass does. Plant mass supports the symbiotic relationship between themselves and the bacterial colonies. If anything, it's the bacteria who do the competing. Having said that though, healthy plants do uptake ammonia, whose production rate is one of the triggers of algal blooms. A high plant mass is better able to attenuate the ammonia production rate and this is very useful in new tank setups, since the ammonia production rate is high due to a lack of established nitrifying bacterial colonies. There is a direct relationship between the stability of a tank and the stability (type and amount) of the bacterial populations.  The symbiosis between plants and bacteria is the key simply because rooted plants support the bacteria.

Now, I don't doubt that this can be accomplished with floating plants alone, but since there is no contact with the sediment and the floating plants they cannot possibly be as effective with regard to the sediment bacteria. The oxygenation rate of the sediment cannot be as high without root interface. Rooted plants send oxygen from leaf to roots which escapes into the sediment thus oxygenating the sediment and supporting a higher nitrifying bacterial population in the sediment. These bacteria then make nutrients available to the plant roots. Without this interface the probability of oxygen starvation in the sediment is much higher which leads to a higher probability of stagnation because when there is low oxygen content in the sediment other bacteria arise which convert ammonia via other elements such as sulphur. So instead of nitrate or nitrogen gas being produced, there is a greater likelihood of noxious compounds such as Hydrogen Sulphide being produced in the sediment. While floating plants do contribute by ammonia uptake, the oxygenation is limited to the water column alone which can only find it's way to marginal sediment layer.

So I not saying  that an exclusively floating plant tank is doomed to failure, far from it, only that it's a different environment with different dynamics, specifically as a result of the lack of root/sediment interface. So the hypothesis that somehow this would be an alternative configuration in case some other configuration fails is murky because one can fail (or succeed) using either. One would simply fail or succeed for different reasons. I'm not sure how you're defining "failure", so other than algal blooms it's not clear what other failure modes you have in mind. In any case floating plants have a superior advantage over their submerged cousins in that they have full access to atmospheric CO2, which makes them almost bulletproof, almost to the point of being a nuisance. I have yet to see an interesting duckweed show tank, that's for sure.  

I regret that I can't really give any ratios or quantities in terms of floating-to-rooted. It doesn't work that way. It depends on the amount of light, the nutrient scheme, the stocking levels - and an  important factor is aesthetics. One needs to define their goal. What does one want the tank to look like? To me that's the first question to answer. Then, design the other factors around that to make it work.

As regards the necessity of a filter, as D. Walstead has demonstrated, no it's not necessary. I guess the question is "What are the objectives?" Without a set of well defined objectives, configuring a tank in a certain way may be either pointless or fraught with pitfalls. Are you wanting to configure the tank in the Walstead scheme, because that's the way she did it, or did you have your own set of imperatives? Do you want to illuminate the tank with sunlight only, for example? I just think that we each live in our own different world and that it's great to use ideas from others to construct that world to make it prettier or easier, but the ideas have to work for us. Certainly, having a filter is easier than not having a filter, and having rooted plants has better long term implications than not having rooted plants, but either method can work.  

Cheers,


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## jlm (29 Jun 2009)

ceg4048 said:
			
		

> Hi,
> As Dave points out, there is no competition between higher plants and algae because they have totally different requirements. So it really doesn't matter what level of nutrients in in the water, low or high. We can see this demonstrated in tanks all over the world. However, yes, it is a good idea to have a sufficient mass of plants. Again, this is the problem with interpretation of the facts. No mass of plants can possibly compete with algae. This is not what plant mass does. Plant mass supports the symbiotic relationship between themselves and the bacterial colonies. If anything, it's the bacteria who do the competing. Having said that though, healthy plants do uptake ammonia, whose production rate is one of the triggers of algal blooms. A high plant mass is better able to attenuate the ammonia production rate and this is very useful in new tank setups, since the ammonia production rate is high due to a lack of established nitrifying bacterial colonies. There is a direct relationship between the stability of a tank and the stability (type and amount) of the bacterial populations.  The symbiosis between plants and bacteria is the key simply because rooted plants support the bacteria.
> 
> Now, I don't doubt that this can be accomplished with floating plants alone, but since there is no contact with the sediment and the floating plants they cannot possibly be as effective with regard to the sediment bacteria. The oxygenation rate of the sediment cannot be as high without root interface. Rooted plants send oxygen from leaf to roots which escapes into the sediment thus oxygenating the sediment and supporting a higher nitrifying bacterial population in the sediment. These bacteria then make nutrients available to the plant roots. Without this interface the probability of oxygen starvation in the sediment is much higher which leads to a higher probability of stagnation because when there is low oxygen content in the sediment other bacteria arise which convert ammonia via other elements such as sulphur. So instead of nitrate or nitrogen gas being produced, there is a greater likelihood of noxious compounds such as Hydrogen Sulphide being produced in the sediment. While floating plants do contribute by ammonia uptake, the oxygenation is limited to the water column alone which can only find it's way to marginal sediment layer.
> ...




Totally agree that one has to have the objectives clear: in my case it isnâ€™t aesthetics but first ease of maintenance and second healthy growth with lack of algae. Quantity or types of plants or fish or any other consideration do not figure highly in my list of priorities. 

The invaluable advice I am getting from a number of great forums such as ukaps is making me come round to the conclusion that a duckweed-only tank isnâ€™t practicable (not enough oxigenation both in the substrate and in the water column being the main reason), but considering that it usually is a very helpful addition to an El Natural setup it seems that a divided aquarium into separate duckweed and planted areas is probably the best option from the ease of maintenance and health of the ecological biosystem point of view. The division could be a simple bit of plastic or glass attached to the tank walls, perhaps a couple of cm deep (1/3 of an inch), splitting the surface in two areas, say, 50-50 - would this be about right?

I know that usually floating plants are left to drift on the surface, which may be detrimental to whichever plant they happen to sit over. Hence the advantage of keeping them to a specific part of the tank. Or maybe not...

Now, the question of the substrate would need some attention since about half of it would not have the oxigenation provided by plants â€“ ie it would have no planted biomass at all, and little light. The solution would be to put substratum fertilizer ONLY in the half that is going to accommodate the plants, and only gravel (or sand, or nothing, for that matter) in the other half. The result would be half a tank with planted foliage under decent light, and the other half in the shade, under the duckweed and with no plants growing from the soil, thus providing the benefits of oxygenation and protection against algae (hopefully  8) ).


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## jlm (29 Jun 2009)

Brenmuk said:
			
		

> Floating plants provide extra shade and they have the ability to use aerial CO2 so can play an import part in an el natural set up. But what really makes the el naturel style tank is a good rich soil substrate and lots of sunlight.
> If you have a soil substrate then you will need plants to root in it because the roots oxygenate the soil and stop it going anaerobic.



Just one question: is sunlight really essential in an El Natural system? We have little of it over here (London) in winter, and it is said to encourage algae. Would this sort of setup work mostly with artificial light? I was hoping to place the new tank in a corner sheltered from direct sunlight, but receiving plenty of reflected natural light - when there is some!



			
				Brenmuk said:
			
		

> I have had 2 outbreaks of BGA in my tank and both I associate with rampant growth of floating plants causing low nitrate levels (the bga first appeared on the roots of water lettuce). So I am wondering if a tank based on floating plants alone can be a balanced tank.



Ugh! Do you think you might not have had those algae outbreaks should you have contained the floating plants to a reasonable level? And what would this 'reasonable level' be, in your opinion?


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## Brenmuk (29 Jun 2009)

I'm not sure if sunlight is essential but Diana Walstead recommends it - she and a number of others who have set up NPT have their tanks next to a south facing window -but plenty have also set up succesful tanks without direct sunlight you might want to quiz her on the APC forum. Her reasoning (if I recall correctly) is that algae is not able to take advantage of higher light intensity to the same extent as higher plants. Direct sunlight is blamed for causing algae growth but in an el natural set up especially an established one this is less of a problem - i think it has to do with bioavailabity of iron (i need to re read her chapter on bio availability of iron - my memory is a bit rusty  :?  on her explanation ).

I have found certain floating plants just grew too rapidly in my set up on 2 separate occasions -water lettuce and riccia - in both cases their rampant growth seemed to coincide with an outbreak of BGA indeed the BGA started to form on the trailing roots of the water lettuce. In both cases I ended up removing the floating plants and that stopped the BGA. I didn't remove all the riccia but it never seemed to dominate again and vanished from my tank. I don't think floating plants per se are problematic - i currently have duckweed and salvinia and they grow slowly. 

In an el natural style tank the plants get their nutrients from the substrate and fish food/waste so nutrients are limiting, if you have a plant that grows super fast and uses up nutrients quicker than they are comming into the tank you will get deficiencies that lead to algae outbreaks. You can then either supplement the tank with additional ferts and possibly CO2 to compensate or you can prune/remove the thuggish dominant plants. I prefer to prune/remove so that there is less maintenance.


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## jlm (29 Jun 2009)

Brenmuk said:
			
		

> I'm not sure if sunlight is essential but Diana Walstead recommends it - she and a number of others who have set up NPT have their tanks next to a south facing window -but plenty have also set up succesful tanks without direct sunlight you might want to quiz her on the APC forum. Her reasoning (if I recall correctly) is that algae is not able to take advantage of higher light intensity to the same extent as higher plants. Direct sunlight is blamed for causing algae growth but in an el natural set up especially an established one this is less of a problem - i think it has to do with bioavailabity of iron (i need to re read her chapter on bio availability of iron - my memory is a bit rusty  :?  on her explanation ).
> 
> I have found certain floating plants just grew too rapidly in my set up on 2 separate occasions -water lettuce and riccia - in both cases their rampant growth seemed to coincide with an outbreak of BGA indeed the BGA started to form on the trailing roots of the water lettuce. In both cases I ended up removing the floating plants and that stopped the BGA. I didn't remove all the riccia but it never seemed to dominate again and vanished from my tank. I don't think floating plants per se are problematic - i currently have duckweed and salvinia and they grow slowly.
> 
> In an el natural style tank the plants get their nutrients from the substrate and fish food/waste so nutrients are limiting, if you have a plant that grows super fast and uses up nutrients quicker than they are comming into the tank you will get deficiencies that lead to algae outbreaks. You can then either supplement the tank with additional ferts and possibly CO2 to compensate or you can prune/remove the thuggish dominant plants. I prefer to prune/remove so that there is less maintenance.



So it seems that a certain amount of floating plants can be helpful, especially to combat algae, but too much of it can have the opposite effect! A case of trial and error, I imagine.  :?


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## baron von bubba (1 Aug 2009)

would rooted plants that grow out above the water level be an option that would give you best of both?   
seems they've not been mentioned yet?


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## jlm (1 Aug 2009)

baron von bubba said:
			
		

> would rooted plants that grow out above the water level be an option that would give you best of both?
> seems they've not been mentioned yet?



In fact, I do keep papyrus plants in (waterlogged) pots and the the thought has occurred to me to keep them in a fishtank. Problem is, these sorts of plants do not contribute to the aquarium ecosystem other than at substrate level, so are of limited use and they complicate the lighting setup of the tank. 

I do love the papyrus, though, they grow all year round, indoor or out, and look quite elegant. They could be used in a terrarium set up IF there was such a thing as a dwarf papyrus, which I do not think there is...


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## baron von bubba (1 Aug 2009)

jlm said:
			
		

> Still on the subject of setting up a new El Natural tank, it strikes me that an abundance of floating plants - duckweek, water lettuce, etc... - may be the soultion to a dead-easy maintenance aquarim setup: given sufficient quantity, to the point of totally covering the water surface of the tank, would they alone provide enough oxigen for a few fish, and would they consume enough nutrients to defeat any algae growth?





			
				jlm said:
			
		

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emergent plants will help the substrate as you say, more than submerged plants tho, which in turn will help the bacteria and ultimately this will help "defeat any algae growth"

also they will obviously take CO2 for the air rather than the water, so other plants will have more available, therefore being able to have a larger plant mass so will again help fight algae.

at night the plants will release some of the co2 they have taken in during the day, if they have taken more in from the air then surly they will give more back to the water than fully submerged plants also?

so i believe these sort of plant contribute the MOST to an aquarium ecosystem??

ok, so you really need an open tank or at least gaps in you cover! :0)


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## jlm (1 Aug 2009)

"at night the plants will release some of the co2 they have taken in during the day, if they have taken more in from the air then surly they will give more back to the water than fully submerged plants also?"

Correct me if I'm wrong, but I thought the co2 exchange was done through the leaves, not through the roots... In any case, would a papyrus-only setup be enough to maintain the ecobalance with the fish, do you think? If so, the tank itself would  need no extra lighting other than the natural light bearing on the papyrus, or just enough additional light to be able to see the fish. However - lol - such an aquarium would need to be placed on the ground or a little distace above it, otherwise the plants would be too high to benefit from the natural light available in the room (they grow to nearly 2 meters tall). Not comfortable viewing, but the algae would have no chance!


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## ceg4048 (1 Aug 2009)

baron von bubba said:
			
		

> ...at night the plants will release some of the co2 they have taken in during the day, if they have taken more in from the air then surly they will give more back to the water than fully submerged plants also?


Hi, sorry, this is an inaccurate assessment of the basic cell metabolism process. There is no "capturing" and "release" of CO2 in this sense. Plants consume and discharge CO2 at the same time. Plant cells, like animal cells, can only stay alive and function if they are powered by the consumption of the carbohydrate "glucose". One result of the cell's consumption of glucose is the waste product CO2. This process of cell energy consumption is called Glycolysis. This is exactly the same reason why we exhale CO2, to rid our bodies of our cell metabolic by-products, so this can be thought of, even in plants, as respiration. This happens 24 hours per day, not just at night. The advantage of being a plant is that it can produce it's own glucose from external CO2, whereas animals must consume carbohydrates from other sources. Plant glucose production can only occur during the photosynthesis period, and during this period the uptake of ambient CO2 far outweighs the cell ejection of CO2 due to glycolysis, so there is a net consumption of CO2. During the night carbohydrate production is zero but glycolysis must continue so there is a net CO2 ejection. What folks may not realize is that while every single plant cell performs glycolysis - and thus produces CO2, only very specialized cells can actually perform photosynthesis. These cells are called Chloroplast.


			
				baron von bubba said:
			
		

> ... so i believe these sort of plant contribute the MOST to an aquarium ecosystem?? ok, so you really need an open tank or at least gaps in you cover! :0)


None of this is "needed" if the basic rules are followed. I don't understand why everyone assumes there is a different science occurring in a low tech tank. This is no big deal. Keep the lighting low and there will be no problems. Floating plants block light penetration and in effect keeps the water column lighting low. No magic there...


			
				jlm said:
			
		

> Still on the subject of setting up a new El Natural tank, it strikes me that an abundance of floating plants - duckweek, water lettuce, etc... - may be the soultion to a dead-easy maintenance aquarim setup: given sufficient quantity, to the point of totally covering the water surface of the tank, would they alone provide enough oxigen for a few fish, and would they consume enough nutrients to defeat any algae growth?


The correct answer to this is that nutrients don't cause algae. You are not adding plants to rid the tank of nutrients. You are adding nutrients to feed the plants. Algae cannot be defeated, so if you focus on this flawed concept you will always have algae. The idea is to optimize the health of the plants which will automatically result in keeping the algae in their larval stage.


Cheers,


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## jlm (1 Aug 2009)

"The idea is to optimize the health of the plants which will automatically result in keeping the algae in their larval stage."

Wow. This would be the crux of the matter. I wonder if you could please elaborate on just how healthy plants inhibit algal growth? We've established that they don't do it by outcompeting algae for nutrients. In fact, these forums are riddled with people reporting that agae crop up in the most varied circumstances, regardless of water changes, light intensity, etc... The only factor they agree on is floating plants helping to eradicate them.

This problem has been bugging me so long that I would kill (and i bet I'm not alone here) to know th link between plant health and algae.

Thanks, ceg4048


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## baron von bubba (1 Aug 2009)

ceg4048 said:
			
		

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ok so i got the science of it wrong, but by your explanation it still means if a plant use's more co2(because it has access to air) it will also eject more co2 into the aquarium than a fully submerged plant would? therefore in a low CO2 situation would benefit the aquarium more? or am i totally off the mark in thinking this?



			
				ceg4048 said:
			
		

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and while most things may be totally obvious to the "experts" it certainly is not obvious to me who is still at the "beginner" level.
i was under the impression having emergent plants is pretty much a "basic rule" for running a "low tech"/"natural" style aquarium, i guess that assumption is incorrect! :0/
if a healthy growing plant oxygenate the substrate helping the bacteria then thats good, so it stands to reason a plant that is growing better and therefore bringing more oxygen to the substrate will be even better!

if the goal was to set up a tank with little interfierence from the owner tho', to be a more "natural" ecosystem with no additional ferts/co2 and W/C's then while the science does not actually change as such, some of the considerations and methods surely will?

obviously i'm not preaching but looking to be put right rather than continue to have the wrong understanding!


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## baron von bubba (1 Aug 2009)

jlm said:
			
		

> "The idea is to optimize the health of the plants which will automatically result in keeping the algae in their larval stage."
> 
> Wow. This would be the crux of the matter. I wonder if you could please elaborate on just how healthy plants inhibit algal growth? We've established that they don't do it by outcompeting algae for nutrients. In fact, these forums are riddled with people reporting that agae crop up in the most varied circumstances, regardless of water changes, light intensity, etc... The only factor they agree on is floating plants helping to eradicate them.
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i asked clive pretty much the same a while ago, here is his reply.



			
				baron von bubba said:
			
		

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				ceg4048 said:
			
		

> Hi,
> "Plants competing with algae" is another myth generated in The Matrix. This is like saying that elephants compete with mice. There is no way any plant can compete with any algae. They would lose. They do not share the same niche. Like elephants, plants require thousands of times more nutrients than algae. That's why the only way to ensure that a plant does not suffer phosphorous starvation for example is to dose 3 part per million PO4 per week, yet, algal blooms can occur at PO4 concentrations of less than 0.3 part per billion - a 10,000X difference. There is no competition with such a lopsided difference in nutritional requirements. In fact, when the plant become malnourished it starts to decay which actually releases not only ammonia, but Nitrogen and Phosphorous back into the water column due to disintegrating proteins and enzymes (which are constructed of Nitrogen and Phosphorous). So algae don't require anywhere near as much nutrition, and when the plants starve algae then have a ready made source of nutrients as well, so they are bulletproof.
> 
> Thinking about plants versus algae in terms of a competitive environment is the worst way of trying to understand the dynamics of the two and can lead to bad decision making if followed even to it's most logical path. That's because this assumption is fundamentally flawed. It's better to think in terms of antelope versus vulture. The vulture senses weakness and death of the antelope and attacks when there is an advantage. A vulture would never attack a strong and healthy antelope.
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## ceg4048 (2 Aug 2009)

baron von bubba said:
			
		

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Well, no, not far off. Your thinking is in the right direction, and starting a low tech tank off as a sort of Palludarium might actually be a pretty nice idea. Ultimately though, this works similarly as with floating plants. The external portion of the plant produces a larger share of the food and oxygen, but most of the gaseous interchanges will occur in the atmosphere, where those leaves are, not in the tank water. I'm sure there is some oxygen transportation to the sediment so this will definitely benefit the substrate bacteria - much more so than with floating plants, which do not interact directly with the sediment. The leaves that are submerged will still not produce as much O2, will not consume as much CO2 and will be shaded by the foliage above so this will effectively lower the lighting.



			
				ceg4048 said:
			
		

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Well, I'm probably the worst person in the world to answer this question because I don't really buy into any of the seemingly "Holistic" philosophy many of the El Natural devotees tend to subscribe to. For example, what does "natural" really mean? In nature there are nutrient rich ecosystems where growth is amazing and where biodiversity is at a pinnacle, and there are nutrient poor ecosystems where the creatures barely eke out a living. The ecosystems of the Marianas Islands or the New Guinea Coral Reefs are constantly fed high nutrient levels from decomposed plant and animal debris deep on the ocean floor and from far away. These nutrients are sent to the surface by slow ocean floor currents. Massive levels of NPK travel up the submerged mountain sides and feed planktonic life forms, which in turn, feed fish, which feed bigger fish. Absolutely NO life is possible without NPK. Plants and animals merely adapt to low nutrient environments. It's not necessarily that they prefer it so.

At the end of the day there is nothing natural about a fish tank. It does not have the biodiversity, the dynamics, the size, nor the stability to be compared with any natural system, however it does contain natural processes which are inevitable. But consider this, is avoiding algae in such a tank "natural"? No, not really, algae is just as natural as anything else in that tank, but we don't like it so we manoeuvre to eliminate it. Why is that OK, but yet adding nutrients/CO2 considered an interference? 

In any case (correct me if I'm wrong), unless it's written somewhere in a Walstead book, I'm not aware of the emergent plant being a requirement of a low tech startup - but neither is it banned, and it sounds like a darn good idea to me!   

Cheers,


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## Brenmuk (3 Aug 2009)

I have often wondered how plants suppress aglae growth. The theories I have come across so far are

1)Competition for bio available iron in the water column which is usually in short supply
2)Allelopathy - chemicals released by plants that inhibit algae growth (all sorts of organisms can release allelopathic chemicals not just plants).
3)The latest from Ceg4048 is competition for ammonia.

One thing I have found is simply having plants in the aquarium is not enough they have to be growing to suppress algae.


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## baron von bubba (3 Aug 2009)

Brenmuk said:
			
		

> I have often wondered how plants suppress aglae growth. The theories I have come across so far are
> 
> 1)Competition for bio available iron in the water column which is usually in short supply
> 2)Allelopathy - chemicals released by plants that inhibit algae growth (all sorts of organisms can release allelopathic chemicals not just plants).
> ...



for what my opinion is worth, 
i think the iron thing is like nitrates and phosphates in the way they are blamed for causing algae but actually dont, they can possibly make an out break worse if at "high" levels after something else, ie ammonia triggers it.

as for allelopathy, while i think in some cases it may be an influence, more so in low tech, no/low water change tanks. it probably has little or no effect in tanks that have regular/large water changes.
think about all the types of plants ppl have together, if the effect was that great it would be harder to mix all the plants we do.
of course i could totally wrong and in fact it's the key to everything!


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## Brenmuk (3 Aug 2009)

baron von bubba said:
			
		

> i think the iron thing is like nitrates and phosphates in the way they are blamed for causing algae but actually dont, they can possibly make an out break worse if at "high" levels after something else, ie ammonia triggers it.
> 
> as for allelopathy, while i think in some cases it may be an influence, more so in low tech, no/low water change tanks. it probably has little or no effect in tanks that have regular/large water changes.
> think about all the types of plants ppl have together, if the effect was that great it would be harder to mix all the plants we do.
> of course i could totally wrong and in fact it's the key to everything!



I know what you are saying about water changes throwing a spanner in the works for the allelopathy theory (using carbon in filters might also counter this theory as well) and assuming that iron is like all the rest of the major nutrients in that more not less is beneficial then its tricky to see how plants can suppress algae growth. If you accept the idea that algae are low light low nutrients scavengers then why don't they grow along side plants in a tank that is for example having ferts added - you would think there is enough ferts for both algae and plants to grow side by side.
This leaves 3rd theory -competition for ammonia - but surely you could argue that an efficient filter would be able to remove ammonia? Also ammonia is constantly being produced by fish etc why isn't there a constant growth of algae?

[Edit] I've just googled this question and found some good articles by Tom Barr who makes a convincing arguement for ammonia as being the trigger for algae growth. I'm sure i've googled this before i suppose it goes to show the effect of putting certain phrases into google!


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## baron von bubba (3 Aug 2009)

Brenmuk said:
			
		

> I know what you are saying about water changes throwing a spanner in the works for the allelopathy theory (using carbon in filters might also counter this theory as well) and assuming that iron is like all the rest of the major nutrients in that more not less is beneficial then its tricky to see how plants can suppress algae growth. If you accept the idea that algae are low light low nutrients scavengers then why don't they grow along side plants in a tank that is for example having ferts added - you would think there is enough ferts for both algae and plants to grow side by side.
> This leaves 3rd theory -competition for ammonia - but surely you could argue that an efficient filter would be able to remove ammonia? Also ammonia is constantly being produced by fish etc why isn't there a constant growth of algae?



this is the way that i understand it...... 
the plants will be working with the bacteria in ridding the tank of ammonia and the bacteria colony will only grow as big as it needs to, if plant growth halts/slows for any reason, ammonia can rise before the bacteria colony grows suitably large enough to deal with it.
in a higher light situation this can happen pretty quick, i think a lower light tank is more forgiving.

i'm sure someone will put me right or at least put it more eloquently.


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## JamesC (3 Aug 2009)

I don't think it is quite so simple as saying ammonia triggers algae. Have too much then yes it does cause problems but many people add ammonium to their tanks daily. Those that add TPN+ actually add fairly large amounts of ammonium and I myself add urea daily. Nearly all commercial products that add N have that N in ammonium or urea compounds alongside nitrates. Perhaps the plants gulp it up so fast?

James


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## ceg4048 (3 Aug 2009)

As James indicates, it's not as simple as just having ammonia. The ammonia production rate and removal is a factor, lighting is a factor, temperature is a factor, CO2 and there may be other contributory factors such as O2 levels. Algae flowers from spores. The sensing mechanism of the spores is still not fully understood, we only have high correlation between their appearance and the known factors listed above. It is not enough to simply have plants in the tank. There is a relationship between the plants and the resident bacterial population within the water/filter/sediment. I would say without a shadow of a doubt light is THE single biggest factor. When the lighting is extremely high you don't need very much of any of the other factors to trigger blooms. As the light energy is lowered however these other factors become more influential. When the lighting is zero the other factors again become irrelevant and no algae is triggered. One can then hold the lighting constant and vary the other factors to get different combinations to trigger the blooms.

Healthy plants increase ammonia removal rate by direct ammonia uptake. They also grow more quickly and deter algae from forming on their surface. They also oxygenate the water and sediment thereby increasing the resident bacterial population. This magnifies the nitrification rate on all levels further increasing the ammonia removal rate. Of course you need a high plant mass to have a significant impact on the removal rate, and of course you need a mature tank in order to have a sufficient bacterial biomass to have a significant impact on ammonia removal rate. That's why new tanks are at greatest risk as they usually lack one or the other. When the tank is then illuminated with high lighting this exacerbates the problems. If there is severe imbalance biomass, then even low tech tanks are susceptible to blooms.

Unhealthy plants are a liability in a tank because their cells die and decay which amplifies the ammonia production rate and does nothing to help the removal rate. Algal armies then colonies and attach to their surface to feed on the nutrients erupting from the dead and dying cells. This is why the blooms attack the plants directly. Unhealthy plants support less bacteria so that bacterial nitrification is also attenuated. Bad combination basically.

Until further data is available I've drawn the tentative conclusion from Barr's explanations that the ammonia laced nutrient products (in some cases) either are not dosed at a high enough NH4 concentration level to significantly disrupt the production/removal equation, or, if dosed regularly and are at high levels, will simply cause a sufficient rise in the itinerant bacterial population which then oxidize the ammonia to nitrate in addition to simple plant accelerated uptake of NH4. Urea addition is addressed by the urease which is in abundant supply in the tank and which acts very quickly.

Cheers,


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