# EI and water changes



## Tim Harrison (9 Dec 2011)

What is the general consensus of opinion out there regarding the use of the frequent and large water changes employed by eutrophic dosing methods such as EI. Is it to rid the tank of the supposed build up of metabolic waste products of plants, due to elevated rates of photosynthesis, or is it to reset nutrient levels to prevent build up thereof? Or none of the above?


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## spyder (9 Dec 2011)

I think this has come up in a few threads recently. If I happen to stumble on them again I'll link them up here for you.


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## Tim Harrison (9 Dec 2011)

Thanks


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## spyder (9 Dec 2011)

And to answer your question I would lean towards removing waste but not just from plants. Diluting nutrient levels just happens to come as part of the package.


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## Tim Harrison (9 Dec 2011)

Thanks for that, but I am still a bit puzzled, though. Although I am sure you are right to an extent it doesn't necessarily explain the disproportionately large water changes (50% or more per week) typically advocated by such methods as EI?


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## milla (10 Dec 2011)

EI is a fert regime therefore the only reason for large, regular water changes is to reset nutrient levels to prevent build up thereof.

The basic principle of EI is to always provide more ferts than the plants can consume.  Thus to prevent build up to toxic levels a reset is required.  

However as a added bonus of EI by doing the water changes you also reduce the build up of metabolic waste products of plants, due to elevated rates of photosynthesis.


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## Tim Harrison (10 Dec 2011)

> However as a added bonus of EI by doing the water changes you also reduce the build up of metabolic waste products of plants, due to elevated rates of photosynthesis.



Hi thanks for confirming that. It's as I thought, however, I do struggle a bit when it comes to this whole thing about metabolic waste products of plants. I would be very curious to know what these waste product are exactly, and how they come to be secreted, and by what mechanism etc.

I may be over simplifying things a bit but isn't the primary waste product of photosynthesis O2? And don't plants store all the other products of photosynthesis in vacuoles for later use, as food, and to convert into chemicals for defence against herbivory, and to inhibit algae and other plants etc?


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## gmartins (10 Dec 2011)

Hi,

I believe that plants (maybe not all) do secrete substances other than O2. Chemodefence against predators or even agaist other plant competitors is a common thing in natural ecosystems. 

I know that marine brown algae such as fucoids have lots of secondary metabolites that are used against herbivore grazers such as littorinids. I also know that some Acacia trees use these substances against herbivores (giraffes) in the African plains. I would imagine that the plants we use in our tanks are no different.

Just my two pence,

GM


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## foxfish (10 Dec 2011)

I have no scientific evidence or explanation, I have read several thousand threads on various forums though!  :? 
It would seem that regular large water changes are effective, whatever the reasons.
I could say that this only seems to apply to high energy tanks with fast growing plants & with lower light, non C02 tanks not requiring or perhaps needing, the large water changes - or so I read.

From my own personal experiences, I know for a fact that if miss two consecutive water changes, algae will appear & may take a month to disappear.
I agree it would be nice to know the true scientific reason why the large water changes are so effective?


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## Tim Harrison (12 Dec 2011)

Thanks guys for taking the time to share your thoughts



> From my own personal experiences, I know for a fact that if miss two consecutive water changes, algae will appear & may take a month to disappear.



I think that the above could perceivably be used as evidence to support the supposition that *disproportionately* (and the key word is "disproportionately") large water changes, typically 50% or more, advocated as part and parcel of eutrophic dosing methods such as EI are to reset nutrient levels, to prevent build up thereof, and the subsequent imbalances that can kick start algal blooms, for instance. 



> I believe that plants (maybe not all) do secrete substances other than O2. Chemodefence against predators or even agaist other plant competitors is a common thing in natural ecosystems.



Undoubtedly, they also remove the toxic substances of fish respiration as well, but as for plant secretions, I am afraid I remain very sceptical. I doubt that even under accelerated photosynthesis substances such as allelochemicals will be produced in sufficient quantities to impact on an aquarium, especially in the space of a week or so.

Further, it is possible to tweak EI to a point where the input of nutrients can be reduced to a minimum whist still providing non-limiting nutrient availability to plants. This in turn means that you can reduce water changes from say once a week to once every two weeks or more. Surely this is further evidence that the *disproportionally* large water changes are to reset nutient levels and not to remove the toxic products of fish or plant metabolism, should the latter exist? If they were to remove toxic products of metabolism wouldn't a weekly water change, of say 15% to 20%, be sufficient?


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## GHNelson (12 Dec 2011)

Hi
Do very little water changes and gravel cleaning when your dosing Co2 and supplementing fertilizers and you will see the results in a few weeks.  
The evidence will be before your eyes.....and it wont be that pleasing.
Remember you are trying to replicate the flow of a stream,river or lake where the build up of excess materials are dispersed/removed continuously....by the local means necessary to cleanse the natural habitat. 
Cheers
hoggie


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## John S (12 Dec 2011)

Hoggie, I always thought gravel cleaning was discouraged with planted aquariums, what issues can it cause? I don't want to find out myself


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## foxfish (12 Dec 2011)

Another observation - withing an hour after lights on, after a large water change, the plants will pearl like no other day. 
I believe this to be due to the additional C02 contained in the fresh tap water?


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## Matt Warner (12 Dec 2011)

> Another observation - withing an hour after lights on, after a large water change, the plants will pearl like no other day.
> I believe this to be due to the additional C02 contained in the fresh tap water?



Hi, I don't think they pearl because the tap water contains a lot of co2. It is more because the tap water contains a lot of oxygen and when you pour the water into the tank, you oxygenate the water more. Because the tank then has a much higher oxygen content, the water is then at saturation point with oxygen, hence the pearling.
When I do my weekly water change, my drop checker goes from a dark green to blue. If the tap water had a high CO2 content, then the drop checker would go more green after a water change, not blue.


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## Tim Harrison (12 Dec 2011)

> Do very little water changes and gravel cleaning when your dosing Co2 and supplementing fertilizers and you will see the results in a few weeks.
> The evidence will be before your eyes.....and it wont be that pleasing.
> Remember you are trying to replicate the flow of a stream,river or lake where the build up of excess materials are dispersed/removed continuously....by the local means necessary to cleanse the natural habitat.
> Cheers
> hoggie



I was wondering then, how do low energy lacustrine environments and other standing water bodies such as ponds with very little if any water movement fit that theory? I always thought that it was the macrophytes themselves that cleansed the water rather than adding further waste products? And why then have purpose built wetlands been used as sinks for purifying water for decades? Just curious.


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## foxfish (12 Dec 2011)

Hi Matty, that is interesting & quite contradictory to what I have read numerous times on different forums including this one!
So the plot thickens...... :?


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## Tim Harrison (12 Dec 2011)

> Do very little water changes and gravel cleaning when your dosing Co2 and supplementing fertilizers and you will see the results in a few weeks.
> The evidence will be before your eyes.....and it wont be that pleasing.



Could it be that what aquarists are actually witnessing, in their higher energy tanks at the end of the week, is the effect of an unhealthy imbalance in excess nutrient levels due to eutrophic dosing and preferential nutrient uptake?


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## foxfish (12 Dec 2011)

What I see in my tank every day, are the plants pearling or producing bubbles from the leaves & stems, what I see after a large water change is a lot more of the same effect?


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## Tim Harrison (12 Dec 2011)

> What I see in my tank every day, are the plants pearling or producing bubbles from the leaves & stems, what I see after a large water change is a lot more of the same effect?



That could fit with my theory since a water change will reduce the effect of any imbalance and kick start photosynthesis anew, especially if they start to pearl, or pearl even more, after the first subsequent nutrient dose.


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## Alastair (12 Dec 2011)

There is also dissolved co2 in freshly changed tap water which is more readily available to plants which is possibly why it pearls so much water change day 


Sent from my iPad using Tapatalk


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## ghostsword (13 Dec 2011)

I have a different experience.

Never done gravel vacuum, never seen the benefit for it.

Dose EI like there is no tomorrow, and do a 50% water change every week. 

Also, co2 into the tank during the day and airstone at night.

Light is kept on for 6 hours, and just two 39w t5s over a juwel 120.

If the excess nutrients caused algae I would be in serious trouble. 

Never had a algae bloom, ad have some bba on wood where there is a bit of flow.

The cause of algae, in my experience, is too much light.


___________________________

I don't know what is the secret of success, but the secret of failure is trying to please the world!


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## gmartins (13 Dec 2011)

I can also say that I have raised my nitrates levels via KNO3 to ~100 ppm in the past to: 1) fight a BGA problem and, 2) to prove myself that excess of nutrients do not necessarily lead to algal blooms. It did not kill BGA (I had to go for a backout) but I didn't cause algae either.

Also I do not test but I am sure that I dose over EI cause it is difficult when you have a 10l tank. Just a bit of bba on old leaves of Staugoryne where flow is really high. Apart from that, the tank is impec.

So, 50% wc may prevent an never-ending scaling of nutrients which may affect the fauna and plants in the end, but I suppose the limits are really high. I also remember Tom saying that there 50% is not a magical number. It could be more, it could be less.

My conclusion is that in high energy tanks, wc are a way of keeping a balance between what we get in and what is produced. I also think that despite all the ferts, plants may benefit from other substances/elements that our water may contain (I'm speculating here).

cheers,

GM


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## Tim Harrison (13 Dec 2011)

You are all absolutely right excess nutrients don't necessarily cause algae, but perhaps an *imbalance* of excess nutrients would. The key word here is *imbalance*. Maybe we can take a lesson from nature and man's influence on natural ecosystems to determine why this is:

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 limit 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 from the water column; 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, and faster CO2 diffusion rates (CO2 diffusion in water is very slow by comparison). The greater availability of CO2 along with higher levels of light intensity 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 a single limiting resource 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, since CO2 is just another nutrient.

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 in our natural ecosystem, 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.

Something else that occurs to me is that the artificial substrates typically used in higher energy set ups have a high CEC which combined with their relatively open and porous structure will lead to rapid absorption of water column nutrients, particularly when combined with the powerful flow rates that are used in such methods; typically 10 times the capacity of the tank per hour. 

*In simple terms, perhaps* this means that it is not just the plants that rapidly strip the nutrients out of the water but the substrate as well; which in turn means that, for some of the time at least, there are probably far less nutrients available to algae in the water column than is typically thought. 

Anyway, regardless of whether there are high concentrations of nutrients in the water column all the time or just some of the time, the point is that perhaps more nutrients are entering the substrate than it is popular at the moment to imagine. Which could also be why the eutrophic dosing methods such as EI work so well when combined with artificial substrates; plants will preferentially uptake most of their nutrients through their roots and in particular phosphorus, which is rapidly absorbed. 

So to consider the idea further, whilst plants continue to photosynthesize nutrients are continually being drawn from the substrate, and replaced by more nutrients from the water column, until the water column becomes exhausted, and then the plants will draw on the reserves left in the substrate until that too becomes exhausted of nutrients. 

If this is so, then perhaps micronutrients also play an extremely valuable role in all this and it is not just because plants need them for growth. The high CEC associated with artificial substrates is down to their large surface area of negatively charged particles (anions). These particles attract positively charged (cations) which in this case are our micronutrients such as iron, copper, and manganese etc, and macronutrients nitrogen and potassium etc. However phosphate is negatively charged and has to bind to positively charged micronutrients to stay in the substrate. In particular phosphate readily reacts with iron. 

However, an imbalance of nutrients means plants will have to work harder to scavenge for those nutrients in short supply and as a result the rate of photosynthesis declines. Further, as the positively charged nutrients are used up in the substrate the negatively charged phosphate has fewer sites to bind too, and is no longer drawn in to the substrate from the water column, where the excess phosphate potentially becomes available to algae. This is especially so since many aquatic plants can not absorb phosphate through their leaves as readily as they can through their roots.

If the imbalance continues photosynthesis will eventually grind to a halt and plants will eventually start to release ammonium due to cellular necrosis, leaving it free to combine synergistically with the remaining excess phosphate in the water column and then…well we already know what happens then.

Anyway to come full circle this is what I meant when I said…’perhaps what aquarists are actually witnessing, in their higher energy tanks at the end of the week, is the effect of an unhealthy imbalance in excess nutrient levels due to eutrophic dosing and preferential nutrient uptake’. 

And that disproportionately large water changes are need on a weekly basis to "reset those nutrient levels", and not, as is popularly believed, to dilute plant secretions. Although to be fair plants release organic acids such as citric, oxalic, and caffeic acids during root respiration but I doubt they would reach toxic levels.


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## roadmaster (13 Dec 2011)

Troi said:
			
		

> What is the general consensus of opinion out there regarding the use of the frequent and large water changes employed by eutrophic dosing methods such as EI. Is it to rid the tank of the supposed build up of metabolic waste products of plants, due to elevated rates of photosynthesis, or is it to reset nutrient levels to prevent build up thereof? Or none of the above?




Can only speak for myself from fishy side of things .
Weekly 50 percent water changes are nothing new, and most folks I know, don't have a problem with this amount and it does provide benefit's to the fish.Been doin it for year's.
I also run a low tech, Low energy tank and dose modified EI as per Tom's Non CO2 method, and change water in 80 gal maybe once a month 50 % Takes all of twenty minutes.
Why would 50 % water change each week be considered diproportionate?


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## milla (13 Dec 2011)

You seem to have strayed from your original question.

You asked why a large weekly water change with EI.   The answer to RESET nutient levels.   That's it.  EI is a fert regime nothing more.

Large water changes which are used by aqaurists in high-energy  tanks to combat algae issues/ remove deitrus / build up of waste is a totally differnt matter and not part of EI.    It is part of tank maintenace.  This can be covered off when you do your water change for EI but can be done whenever you think it's necessary regardless of fert regime.  

It looks to me that you are trying to find a way of running High light / Co2 and water coloumn dosing without water changes / maintenace. IF so you need to look at some older posts on the net refering to PPS-Pro as a dosing method. 
This method is less populat than EI because EI is easier to understand / work with and doesn't require reqular testing of the water in the tank.


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## Tim Harrison (13 Dec 2011)

> Why would 50 % water change each week be considered diproportionate?



Disproportionate in that without the need to reset nutrients levels, perhaps a 15% or 20% water change would suffice, if it was just to rid the tank of the metabolic waste products of fish respiration.


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## JohnC (13 Dec 2011)

I'm not sure what you are arguing here....

What I know is it works, for me and many other high tech aquarium keepers. 

My tap water has between 5 and 9ppm phosphate in it. I have inert sand (mostly) as my substrate. I do EI with the water change and add more phosphate in that dosing as well.

My plants are happy, my fish are happy, i have no algae.

The method is a catch all, its design to take endless testing out of the hobby, as test kits are a waste of money. 

There are other methods, like those advocated by Diane Walstad and obviously yourself from what I can tell from reading your website. Which some people have used to degrees of success.

Yes I could reduce all my ferts downwards to the bear minimum beyond needed uptake, but then if my plant mass increases, my fert absorption goes up and bang I've accidentally triggered an algae outbreak.  

In regard to the water changes, as far as I understand they are for two factors.

1. Remove excess organic waste from the tank. As through *extensive* scientific tests mr Barr et al have show that ammonia *does* cause algae outbreaks. We run closed systems so adding fresh water and cleaning our filters is always beneficial. A big *regular* water change just allows us to practice good fish keeping.

2. Allows the buildup of nutrients to be capped over time at an upper limit that will never be toxic to livestock if adding only the recommended amounts of nutrients per week.  This is important as the EI method is a "catch all" solution for dosing.

Here is a great website showing the effect of that 50% water change on nutrient build up, assuming various levels of uptake. Try modifying the same results for a 20% water change and see what happens.

http://ei.petalphile.com/

Best Regards,
John

edit - a couple of posts happened when i was writing this so it is a little out of sequence.


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## Tim Harrison (13 Dec 2011)

> You seem to hav e strayed from your original question.
> 
> You asked why a large weekly water change with EI. The answer to RESET nutient levels. That's it. EI is a fert regime nothing more.



Thanks for pointing that out, but sometimes things take on a life of their own which are far more interesting to pursue.



> Large water changes which are used by aqaurists to combat algae issues/ remove deitrus / build up of waste is a totally differnt matter and not part of EI. It is part of tank maintenace.



Thanks for confirming that, but it seems that not everyone is as clear on this as both of us are, and I was trying to get to the bottom of why that is. Like I have said before, elsewhere in this forum, there is a lot of pseudoscience out there, most of it an imperfectly understood representation of real science. 

Many just blindly follow without questioning why, simply because that's the way it’s always been done, or simply because they read it somewhere; usually the author is someone who should know better. Take for instance, the UKaps article on EI, it states that water changes are, and I quote '…to remove as much of this organic waste as possible’; which contradicts Tom Barr’s assertion that it is to reset nutrient levels.



> I'm not sure what you are arguing here....



That could be because I'm not arguing anything really, I'm just trying to put other aquarists differing views in to context and try to understand their interpretation of how and why methods such as EI work, mainly for the reasons above. 

Whilst "it" is used simply because it works, it is always good to know why it works, don't you think? since things can go wrong and it's not always for the reasons we have perhaps been led to believe; which in turn can make managing or fixing the problem harder to achieve. For instance if we are aware of the mechanisms which trigger algal blooms we can prevent them before they occur, rather than just blindly following a procedure in the hope that it will continue to serve us well.


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## JohnC (13 Dec 2011)

Troi said:
			
		

> Whilst "it" is used simply because it works, it is always good to know why it works, don't you think? since things can go wrong and it's not always for the reasons we have perhaps been led to believe; which in turn can make managing or fixing the problem harder to achieve. For instance if we are aware of the mechanisms which trigger algal blooms we can prevent them before they occur, rather than just blindly following a procedure in the hope that it will continue to serve us well.



Could not agree more. 

I read for 2 years before trying EI and CO2 and still got every algae under the sun in my first 6 months.  8) 

I'm always learning. But will pay particular attention to certain people's posts on the methods that I use. Especially Mr Barr's whom posts here with excellent frequency.

Here is a post of his which argues almost the same point you are making earlier.



> Re: EI daily methods or PMDD + PO4
> by plantbrain » Wed Feb 03, 2010 1:08 am
> 
> Tropica Master grow = TMG, now renamed to Aquatic plant nutrition traces.
> ...



Best Regards,
John


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## roadmaster (13 Dec 2011)

Troi said:
			
		

> > Why would 50 % water change each week be considered diproportionate?
> 
> 
> 
> Disproportionate in that without the need to reset nutrients levels, perhaps a 15% or 20% water change would suffice, if it was just to rid the tank of the metabolic waste products of fish respiration.




Hmmm, Waste comes from both end's of the fish I keep.
If I've already got the hose,pump,syphon out... I'm gonna change more than 15 to 20 percent.
 I could prolly go much longer in my low tech tank between water changes, but old habit's die hard, and once a month is about all the longer I can stand.(Don't tell Tom)
I have often heard some.. cite the water change each week with EI, as some sort of detriment along with daily dosing.But for me, and maybe other's?,, dosing is no more tedious than feeding the fish each day, and water changes are a no brainer for healthy tank's, the more the better in most cases.
I have lot's of fish and feed them prolly too much and I also dose KNO3,KH2PO4,and trace once a week.
Have seen nothing thus far that would indicate plant's or fish are suffering, and most of all,,no algae that had plauged my past effort's.
Nope,,if the masses of folks that have inspired me thus far, as evidenced by their success, told me I needed to stand on one leg, while wearing a dog turd on my upper lip, and tossing fertz into my tank over my shoulder,to acheive similar results... Well I hope it's a small dog.


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## JohnC (13 Dec 2011)

roadmaster said:
			
		

> Nope,,if the masses of folks that have inspired me thus far, as evidenced by their success, told me I needed to stand on one leg, while wearing a dog turd on my upper lip, and tossing fertz into my tank over my shoulder,to acheive similar results... Well I hope it's a small dog.


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## Tim Harrison (13 Dec 2011)

> Well I hope it's a small dog.



So do I...but a larger one would be much more impressive


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## PeteA (13 Dec 2011)

Really interesting topic and quite nice to see the 50% water change concept discussed as I've been curious on the same subject.  I think the most confusing thing I found is that other (more fish orientated) forums tell you to do smaller/less regular changes and the large changes that go alongside Ei goes completely against this advice.  My biggest gripe with doing 50% changes is the fact I use RO water for the fish (due to poor tap water) and it takes a long time to run it and is a pain to store water in that quantity 

I came to the conclusion that generally every single tank is unique, having different plant types and plant size and I imagine that if somebody actually did a full on research study, different plants will have different nutrient uptakes   Ei takes the approach that it's better to have too much than not enough (verging on sledgehammer approach!).


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## plantbrain (14 Dec 2011)

I think it's important to note that EI does use 50% as a simple starting point, it does not suggest that this is written in stone, that's NOT the purpose.

You start with a safe non limiting amount and progressively TWEAK from there, eg, lower the dosing slow and progressively a little each week, watch the plants, and the algae issues etc.

This way you have a plant that is in good health, and you will see smaller changes and have less risk.
If you start with no dosing or super lean, then you have a stressed plant to begin with, and no real reference point to observe.

This SAME approach to dosing less, can be done, and then once you have arrived at that point for the dosing, then you can reduce the % water changes down, also, the same progressive approach is used.

This way you start safe and have and ensure good growth and less risk, the trade off is initially you do MORE LABOR to keep the tank looking nice. This is true with most any method and with most any new tank or a tank that already HAS AN EXISTING problem. So you are not going to avoid that and there is no silver bullet, only a rational way to rule some things out.

We can acknowledge that there is a known non limiting amount for all plant species for fertilizer.
This is roughly EI. Now many and most species will use less than this amount. But to cover all the bases, we dose a bit more.

With RO, I typically would mix 50/50 RO/Tap or maybe 2/3rd RO to 1/3 Tap if real nasty hard..........but water changes there become a larger concern, but a reservoir can really make all that easier.

If you are interested in accounting for such differences in species and % uptake vs what was dosed for the week, or the effects of build up vs % water changes, per unit time, then Wet/s Modeling calculator will predict the outcomes:
There is even a % fish food added to this model.

http://ei.petalphile.com/

Now what we do not know, is how much is unacceptable and poses a risk to fish/shrimp.
For NO3, it's quite high, 100ppm or more using KNO3..........pretty easy target to hit and avoid going over, for P, it's even easier to hit.


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## ghostsword (14 Dec 2011)

I use the James all in one recipe as a basis, and have tweaked it a bit to add more nitrogen and less potasium, as over a year that was what it gave me a better result.

I really do not see the 50% water change as a way to reset the nutrients, but as a source of fresh water into the tank. The same way I always open a window on my room in the morning, be it raining, snowing or sunny.

The fish an plants are living things and they absorb and release stuff, same as we do, so I am sure that it promotes wellbeing of a tank having fresh water added once in a while.  

I am nit religious with the water chance, sometimes I change less than 50%,  sometimes I wait more than 7 days, but I dose everyday, an average of 15ml on the tank, sometimes more sometimes less. 

I may not be an aquascaper but I can successfully grow plants and so far the above is working for me.  

From my experience I do not think that plants care much about RO water, tried it for two months and saw no difference. The plants grew fine on tap water.

My two cents. 


___________________________

I don't know what is the secret of success, but the secret of failure is trying to please the world!


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## Tim Harrison (14 Dec 2011)

> I really do not see the 50% water change as a way to reset the nutrients, but as a source of fresh water into the tank. The same way I always open a window on my room in the morning, be it raining, snowing or sunny.



Fair comment, I agree to a certain extent, but I also have undying faith in aquatic plants as water purifiers and the subsequent protection it offers fish, especially as some of us have tap water that is less than ideally suited to keeping plants and fish in the first place. 

So to carry your analogy further, sometimes it can be like throwing open your window in the morning and breathing in the smog of a post-apocalyptic industrial landscape, whether it be raining, snowing, or sunny.


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## ghostsword (14 Dec 2011)

true... A hard question to get a general answer as every situation differs from user to user.


___________________________

I don't know what is the secret of success, but the secret of failure is trying to please the world!


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## roadmaster (15 Dec 2011)

I agree,   
I have moderately hard water hard water 10-12 DGH from the tap.
 Over time ,with lot's of plant's, and fewer water changes,, I am able to keep Cardinal tetra's  as the water slowly becomes more acidic through natural process, and smaller less frequent water changes seem's to suit them.
Large water change in this tank,would introduce fishes to water not much to their liking.Have alway's been more in to fish than needs of weed's.
In larger 80 gal planted tank with numerous fishes, and malaysian livebearing snails, I use the larger water change to dilute pollutant's and to maintain the hardness for the sake of the snail's shell's.The snails are important to me. They sift through ,aerate ,substrate as well as to help break down solids thay may be there from fish food's, fish waste.Maybe more than plant's need.


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## plantbrain (17 Dec 2011)

Troi said:
			
		

> > I really do not see the 50% water change as a way to reset the nutrients, but as a source of fresh water into the tank. The same way I always open a window on my room in the morning, be it raining, snowing or sunny.
> 
> 
> 
> ...



This water change issues can easily........go either way. But.........what is the goal of the individual using the a method?

For intensive gardening, I'm going to do more water changes, for new set ups, I'm going to do more water changes, for high fish loads, I'm going to do a lot more water changes, if there is any algae.....more water changes.........

A slower gardening set up with less picky plants and less algae issues, more algae eaters, less light, sediment rich.........I can certainly get away with a lot more flex with respect to water changes.........I do no water changes on my non CO2 tank........input out index of sustainability is near zero for that tank, but the 120 Dutch tank has a high production index, thus is a garden that produces a lot of plants for sale(to offset the labor and added work I do to keep it up). 

If sustainable is the goal, then the non CO2 method cannot be beat.
More intensive gardening? More water changes tends to be the rule. ADA seems to think so, so do I.


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