There he goes again miss-quoting me and taking my comments out of context...he must be a tabloid journalist…Hang on I am sure I qualified my explanation with the prefix in “simple terms”! Lets go back and check…
Troi wrote…
...that in simple terms...
Yep, I was right; there it is in black and light blue.
My simplified explanation was an attempt to avoid recourse to longwinded and overly complicated pseudoscience which is never helpful and rarely informative (I like to keep my pseudoscience short and to the point). Nevertheless, I’ve only got myself to blame, I should have made it clear in my explanation that I was referring to CO2 depletion and its impact on the rate of photosynthesis and therefore nutrient uptake...that is, “in simple terms”, of course. But then in all fairness I wasn’t expecting the unsolicited scrutiny of the Planted Tank Gestapo – “ve have vays of making you talk” - and its Spanish Inquisition type interrogation tactics, but then – Daaaaaaaa...“NO ONE EXPECTS THE SPANISH INQUISITION!!!”. Perhaps I will be better prepared next time I'm poked with a soft cushion.
There seems to be a lot of scientific mumbo-jumbo imperfectly understood by many and not just in the aquarium community (a little knowledge is a very dangerous thing, don’t you know), largely because in science, as in life, there are very few, if any, universal constants. Accordingly, dogmatic devotion to paradigms will land you in trouble every time; but then haven’t we already discussed this elsewhere in the forum?
Put simply, don't believe everything you read, and it's never a good idea to simply regurgitate it, at least not without offering up references to peer assessed scientifically rigorous research.
Whilst I am being philosophical, it is also a good idea to draw breath every now and then and consider what motivates us to do the things we do and why. For instance, do we offer the benefit of our imperfect wisdom out of a desire to inform and serve the greater good, or simply to impress? And what needs of our own are we fulfilling by doing so?
Allow me to elucidate with reference to a treatise critiquing my humble attempts at helping a fellow aquarist.
ceg4048 wrote…
This is a distortion of the fundamental principle of Law of the Minimum…The law specifically describes and predicts the attenuation of GROWTH due to poor uptake (or unavailability) of the least available nutrient. This is an important distinction. The consequences and limitations imposed by unavailability of each nutrient may or may not affect the uptake of other nutrients. It depends on which nutrient is being limited. Shortages of some nutrients do attenuate the uptake of some nutrients. Shortages of other nutrients limit the use of some other nutrients internally but may not necessarily limit their uptake. Further, shortages of some nutrients, primarily Metallic Micronutrients, cause the substitution of other metals which may cause an increased uptake of the substitute metal.
What has been described above is not the Law of the Minimum (LM) but instead synergistic interactions between multiple limiting resources. This is an important distinction. By contrast LM is an earlier paradigm of
single resource limitation. The author of the above quote does not appear aware of this distinction since he seems to regard them as one and the same. Regardless, the net effect of nutrient deficiency is a reduction in primary production, which is the point I was trying to elucidate using LM as a simple example.
ceg4048 wrote…
This is where mumbo-jumbo reaches it's absolute zenith. Nutrients in the water column is NOT why frequent water changes are employed in eutrophic dosing schemes such as EI... These are myths that are perpetrated all over the web from people who only pretend to have a clue about EI.
I am sure Tom Barr (the architect of EI) would be fascinated by his declaration, I quote Tom himself…” at the end of the week you remove nutrient and reset…good sized weekly water changes are an excellent way to do this and avoid build up and any dosing errors”. Pretty conclusive that his water change assertion is wrong; don’t you think? It seems he was a bit hasty in his forecast regarding the absolute zenith of mumbo-jumbo. Perhaps he should revisit his own article and revise it.
If I may be so bold as to make a suggestion as to how? It goes something like this…‘EI is not an exact science, the title “Estimative Index” kind of gives the game away really, so there is an enormous potential for error, especially if you are new to the technique. But do not panic Tom Barr, who first popularized the method, has already thought of that and recommends a large weekly water change to reset the nutrient levels and prevent any harmful effects due to dosing errors.’ Not bad, huh, even though I say so myself.
ceg4048 wrote…
The frequent water changes imposed by EI have everything to do with the elimination of hazardous organic waste. The protein and carbohydrate waste products excreted by the plants are magnified tremendously by the addition of Carbon compared to non-Carbon enriched tanks. These waste products…coat the surface of the plants, which creates a physical barrier to the uptake of CO2 and nutrients. This blockage actually exacerbates nutrient deficiencies especially in tanks which have poor flow and distribution.
So much pseudoscience in one paragraph I barley know where to start. I know lets start with…
ceg4048 wrote…
The frequent water changes imposed by EI have everything to do with the elimination of hazardous organic waste.
Well I think we’ve already established that’s erroneous, so moving on.
ceg4048 wrote…
The protein and carbohydrate waste products excreted by the plants are magnified tremendously by the addition of Carbon compared to non-Carbon enriched tanks.
I would honestly love to review the scientific literature that supports this statement. After all it’s good to learn something new every day. I always thought – and please correct me if I am wrong - that plants break down substances very slowly, this coupled with a distinct lack of any special excretory organs means that the accumulation of plant waste products is highly unlikely to impact on an aquarium week to week or even month to month, even under rapid growth conditions stimulated by CO2 injection, and even without water changes, with a cherry on top. And whilst we’re on the subject, healthy plants utilize ammonium in the water column preferentially to any other source of nitrogen. So the removal of organic waste from fish respiration is not much of an issue either.
Anyway, I hate to labor the point, but back to that old chestnut EI. Tom himself states - and to paraphrase this time – that it is possible to tweak EI to a point where you can reduce the input of nutrients to a minimum but still have non-limiting nutrient availability, or “ppm” as he puts it, to plants. This in turn means that you can reduce water changes from say once a week to once every two weeks or more. Sorry, still no mention of ridding the tank of plant waste derived from photosynthesis or even respiration. Could that be – and forgive me if I am over simplifying things a bit here - because the main waste product of plants is O2?
I am sure I don’t need to spell out the implications of the above for his water change theory. However, if anyone is struggling with the concept I will be more than happy to explain. If I was him I really would revise that article on EI as soon as possible.
Plants do however, produce secondary metabolites such as tannins, resins, essential oils, etc which they may store or use for defense against herbivory and other organisms. For instance, many plants also secrete allelochemicals that inhibit the growth of other plant species, and most macrophyte species secrete allelochemicals that inhibit algae. However, the impact of allelochemicals is usually minimal unless the toxins are secreted en masse by huge populations of the same species, in these circumstances it can prove an incredibly successful strategy. However, in an aquarium I doubt the impact is anywhere near as potent.
Angiosperms and ferns also get rid of waste products by “partial death”, that is, by shedding leaves and branches etc. These can easily be removed from the aquarium without water changes, but there isn’t really a need since as long as the other plants are healthy they will uptake the nutrients released by decay. It’s all part of natures great tapestry of flows and cycles; it’s all quite elegant when you think about it.
ceg4048 wrote…
These waste products…also coat the surface of the plants, which creates a physical barrier to the uptake of CO2 and nutrients. This blockage actually exacerbates nutrient deficiencies especially in tanks which have poor flow and distribution.
At the risk of appearing ignorant…again, I am at a complete loss as to exactly what types of protein and carbohydrate waste products he is referring to? And how come they end up supposedly coating the surface of plants? I thought that, at least in the case of carbohydrates and proteins, most plants stored them in vacuoles. Do they become entrapped in plant coating biofilms instead? Or maybe he's erroneously referring to the Prandtl Boundary layer? Or none of the above? I’m just spit balling here. But answers on a postcard, first correct one gets a prize.
Incidentally, his coat of many colours theory also flies in the face of decades of research and proven practical application in the use of aquatic plants for biofiltration. Surely, the net effect of healthy macrophyte production is water purification, not pollution, or spurious coatings of whatnot that limit photosynthesis and growth?
ceg4048 wrote…
Again, In a eutrophic tank, nutrients are always available to algae. Algae would not have to wait very long in order to have access to nutrients. In fact algal spores are normally sitting on top of plants' leaves as well as in the sediment and in the water column. It could easily be argued that they have access to the nutrients first, because the nutrient would have to pass by them before getting to the plant.
I am sure he could easily argue the hind legs off a donkey, but it don’t necessarily make it so. However, he's already hit upon the answer to this apparent paradox himself, albeit accidentally. Could it have something to do with LM or synergistic interactions between multiple limiting resources, after all? That was neat we’ve come full circle I love it when that happens; kinda like fashion and trends.
ceg4048 wrote…
What makes this theory of nutrients causing algae even more absurd is that immediately after changing the water, EI dosing schemes require that you immediately does the tank, so that the nutrient levels rise to eutrophic levels immediately. Algae do not have to wait around for plants to finish their feast. They can have a feast before the plants can ever get to them if they are as efficient as you say. So why don't my EI dosed tanks have algae?
Well I don’t want to appear rude, or overly judgemental, but I think that we have firmly established that in his case it’s quite obviously more by luck than judgment; but nevertheless read on and I will explain.
It is still a highly contentious issue but in nature the limiting factor to the growth of algae is phosphate. Naturally occurring levels of phosphate in unpolluted water are very low, typically between 0.003 and 0.02 mg/l. Let’s call it nature’s way of maintaining ecological homeostasis. Input of anthropogenic waste such as detergents can rapidly upset this homeostasis by increasing levels of phosphate and other nutrients such as nitrogen, and shazam, before you know it a positive feedback loop degrades a healthy and balanced ecosystem in to an algae paradise. In fact research has shown that in particular nitrogen and phosphorous in freshwater systems show some type of synergistic response to this end.
In the aquarium the level of phosphate is typically much higher, especially if you are using eutrophic dosing methods such as EI. But that’s usually ok, all other parameters being equal, as long as other macronutrients and micronutrients are in balance and supplied in quantities that ensure no limits to plant growth (both excess and deficiency can retard growth). Under these conditions macrophytes are able to out-compete algae starving them of phosphate, which, lets not forget is an essential nutrient. CO2 injection reinforces this effect leading to rapid removal of nutrients, and especially phosphate, from the water column. And to throw his quote back, that is why “massive nutrient levels result in the reduction of algae”.
A similar phenomenon is often witnesses when floating plants are introduced to lower energy planted tanks overrun with algae or algal blooms. The tanks soon become cleansed of algae often within a matter of weeks or months. Floating plants have the “aerial advantage” that is they do not compete with algae for water column CO2 because they can take advantage of relatively high atmospheric concentrations of CO2 along with higher levels of light intensity which together promote higher levels of photosynthesis allowing them to efficiently remove excess nutrients form the water column.
However, because macrophytes are more complex organisms than algae, if nutrient levels are out of kilter then LM or synergistic interactions between multiple limiting resources prevent them form utilizing the phosphate and it becomes available to algae. And why for instance, a hiatus in CO2 injection can also result in an algal bloom. See what I did there, yep I closed that circle again.
Further, if the hiatus continues macrophytes will start to decay and release ammonium which combined with high levels of phosphate can kick start algal blooms; which we have already established. Then add in to the mix continued nutrient dosing and the addition of relatively phosphate rich fish food, and shazam, you have a positive feedback loop not that dissimilar to the one already described above, and it’s all down hill from there on out.
However, that aint the whole story, there are a whole load of other factors which may contribute synergistically in one way or another, such as iron availability or excess, and allelopathy. In particular some species of algae have also been known to produce allelochemcicals that inhibit macrophyte growth under eutrophic conditions, but this strategy only really becomes a problem when the little blighters are in the ascendancy.
In addition, sometimes the methods employed to reduce algal blooms can exacerbate them once they have become established for instance light reduction. Most algae are shade tolerant organisms so lowering the light intensity can give them the advantage over many photophilous macrophytes particularly considering the above synergistic interactions between multiple limiting resources.
ceg4048 wrote…
And why wouldn't Liebigs Law also apply to algae?
Finally, in answer to this last question. Liebig’s law of the minimum led to a massive increase in agricultural crop yields, the purpose for which it was originally intended. It has long since been hijacked by other scientific disciplines to explain growth in populations and markets etc. Nevertheless, Liebig is best known as the farther of the fertilizer industry, so all proponents of the higher-energy end of the hobby owe him a great dept of gratitude. But when all said and done I have to confess that applying Liebig’s law of the minimum to algae is perhaps stretching it’s original purpose somewhat; but the principle still applies, I think the above adequately describes why.
Hope that helps