# EI Natural v. Low Tech



## bugs (23 Sep 2007)

The two topic areas within the forum got me wondering:

1. What is the difference between EI Natural and Low Tech? (Perhaps a sticky in each would be a good idea).

2. What does the "EI" in EI Natural stand for?

Cheers


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## Matt Holbrook-Bull (23 Sep 2007)

1. Natural methods are methods that dont use any filtration other than the plants themselves. It goes deeper than that but thats the crux of it.

low tech tanks are those without co2, generally low light as well with plants to match those conditions.


2. the El bit is saying it as if you were french! like 'el naturel


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## Ed Seeley (23 Sep 2007)

IMHO, El Natural means tanks that have a soil substrate and infrequent (twice yearly (!) or so) water changes coupled with decent fish load, no CO2 and only mechanical filtration, apart from the plants as Flora said.

I'd say Low tech would be a broader church of all the types of system that use no CO2 (or maybe DIY) with various substrates, little fertilisation and low to medium lights.
As the lighting gets higher and things like CO2 are added I suppose it gets 'higher' tech!


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## bugs (23 Sep 2007)

Interesting how this is unfolding...

I'm treating El Natural  as:
> No CO2
> No added ferts
> Fairly basic filtration*

As for lighting... Diana Walstead recommends 2-3wpg which I would regard as mid to low end of the high light category.

* For my transition to El Natural in my 60cm, I'm flexing the above slightly in that I'm going to continue using my Eheim 2324 Thermo filter. I'm hoping that it does not have any adverse effect.


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## Matt Holbrook-Bull (23 Sep 2007)

bugs said:
			
		

> As for lighting... Diana Walstead recommends 2-3wpg which I would regard as mid to low end of the high light category.



I didnt even have that in a high light, high tech tank.  3 wpg is extremely high lighting.

Diana is a member here, maybe if your reading Diana, you can give us your take on it all?


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## GreenNeedle (23 Sep 2007)

Read the novel below


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## ceg4048 (24 Sep 2007)

bugs said:
			
		

> The two topic areas within the forum got me wondering:
> 
> 1. What is the difference between EI Natural and Low Tech? (Perhaps a sticky in each would be a good idea).
> 
> ...



bugs,
          One could get an advanced degree tackling question number 1. I'm much more confident answering number 2 so I'll tackle that one. E.I. stands for Estimative Index, which by itself means nothing. To get a grasp on what this really means it's necessary to understand a little bit how aquatic plant husbandry evolved over the past two decades before the advent of the technological inovations that we now take for granted. 

You'd need to read articles on the krib, http://www.thekrib.com/ THE reference aquatic plant hobbyist site for a generation. The mechanisms of plant physiology and nutrient transport were only vaguely understood. The struggle was to determine just exactly how much of each nutrient was required and at the same time to determine the causal factors of algae. That period was characterized by the belief that the key to limiting algae was to be found in the limiting of nutrients. The search was on to find the minimum level of nutrients that would benefit plants but that would "starve" algae. During this time the focus was more on nutrient uptake via roots. It was also in vogue to depend on NH4 generation as a viable source of nitrogen. As the improvements in lighting technology increased so did the proliferation of algae. We have to remember that 20 years ago there were no T5s and reflectors were hardly used. The fluorescent bulbs available at the time had meager outputs compared to what is available now so that 3-6 wpg would hardly have been super high in modern terms.

It was slowly discovered that CO2 was a benefit, however the water column nutrient issue was still not resolved. Tom Barr through his available empirical data and experimentation concluded, among other things that;

1. algae were more adept and quicker to respond to environmental changes than higher order plants.
2. as a result, limiting nutrients in the water column was not a viable method of controlling algae.
3. aquatic plants can and do feed quite readily from the water column, and in many cases feed preferentially from the column.
4. plant growth is restricted by limiting water column nutrients.
5. maximum growth can only be obtained when there are nutrient concentration  in the water column equal to or beyond the maximum uptake rate of each nutrient.
6. algae cannot be induce by nutrients alone.
7. nutrient deficiency causes failing health in plants which in turn was correlated with the inducement of algae due to decay.

The "Estimative Index" therefore is an attempt to estimate what the maximum possible uptake rate is if all factors are non-limiting. That means maximum light - at what point does adding more light not result in increased growth. Maximum CO2 - at what point does adding more CO2 fail to produce increased growth etc. etc. The values of each parameter became the  index or reference value that would ensure that on any given day, at maximum growth rate and at maximum uptake rate the concentration in the water column exceeded this maximum uptake rate (non-limiting ). If memory serves, the standard dosing values were calculated for a 20 gallon (US) tank at 5-6 wpg. Dosing for other tank sizes scale linearly.

Therefore if you lower any of these parameters from the maximum achieved you will be limiting growth, however you are limiting from a MAX growth perspective. As you lower the light and keep all other things at max levels, this is called light-limiting. As you lower the CO2 and keep other things at max levels the tank becomes CO2 limited etc. The idea though is that light is THE uptake driver so that lowering the light lowers uptake of all other things proportionally. Light limiting does not have the negative consequence of Phosphorus limiting or Nitrogen limiting.

Because of the belief in the above items 6. and 7.  the maximum required nutrients are dosed even if the tank is light is limited. This is done so that it is unnecessary to repeat the experiment under limiting lighting and to determine a new set of dosing schemes for 4 wpg, 3 wpg etc. You are therefore "Estimating" the dosing based on non-limited lighting. It's also  an estimate in the sense that you never need to measure the concentrations via test kits. You are dosing an estimated amount based on max uptake rate, not on actual uptake rate since this rate will actually be lower.

Fundamentally therefore the EI methods, whether high tech (high light, high CO2) or low tech (low light, low CO2) focus more on inorganic dosing, whereas perhaps Ms. Walstead's methods focus more on substrate uptake and organic water column dosing via the fauna. In this sense Barr's low tech methods probably only differ from Ms. Walstead's in his use of the inorganic supplementation.

Hope this helps.

Cheers,


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## Keith (25 Sep 2007)

Well it certainly helped me. Thanks you very much for such a lucid explanation.


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## Ed Seeley (25 Sep 2007)

It's not E.I., it's El (EL), as in rather bad french pronunciation.  From what I understand it started of as a little joke and kinda stuck.
Flora said this in an earlier post.

If you want to read more about 'El Natural' look at this thread on APC.  Diana is a very regular visitor there and the ideas seem to be based around her book, 'The Ecology of the Planted Aquarium'
http://www.aquaticplantcentral.com/forumapc/el-natural/26458-what-el-natural-step-step.html


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## bugs (25 Sep 2007)

E.I. (as in Estimative Index) is the method that I am currently using. It's the "El" in "El Natural" that had me confused - I thought it was initials but I get it now. Cheers.


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