Re-re-re-evaluating my EI dosage

[magnosis]

Maybe I'm looking at this too much from a mathematical point of view and not enough from a try-see-and-adjust perspective... but I'm having a hard time consolidating what people refer to as "suggested" EI dosage.

I have made an Excel spreadsheet to calculate the resulting PPM from suggested EI dosages I found on 3 or 4 different sources. The differences are notable from one source to another - between the Fertilator, Rota.la, Tom Barr, Rex Grigg and one consolidated thread on TPT.

Maybe I should publish that spreadsheet

Maybe it doesn't matter if my dosage is 20% off... but when I look at http://rota.la/ for the fert buildup over time chart, I feel like this should not be taken lightly.  I'm really concerned about the 'ticking time bomb' effect of EI dosage in the long term, and feel like I should be very careful not to over dose.  50% WC will only flush out 50% of the excess. It's simple math that the excess will build up over time.

So I will [re]start by asking this:

When you start a new planted tank with E.I. dosage, do you start by dosing, say, half of the recommended, then adjust up when you notice deficiencies, or do you start with the suggested dosage, and reduce dosage until you see deficiencies?

[exv152]

Maybe it doesn't matter if my dosage is 20% off... but when I look at http://rota.la/ for the fert buildup over time chart, I feel like this should not be taken lightly.  I'm really concerned about the 'ticking time bomb' effect of EI dosage in the long term, and feel like I should be very careful not to over dose.  50% WC will only flush out 50% of the excess. It's simple math that the excess will build up over time...

Magnosis, Over the years I've read tons of stuff regarding fertilizer dosing, but I've never come across anything that would suggest there's a ticking time bomb with ei. Can you point me to a thread or source that would explain this in more detail? Thanks

[fischkopp]

That time bomb can be disarmed if you stick to 100% water changes. 

[magnosis]

Can you point me to a thread or source that would explain this in more detail? Thanks

http://rota.la/ei/
While this is pretty light on documentation, it shows the accumulation over time if you do any less than 100% water changes.

With the Estimative Index, we are dosing an excess of nutrients such that they never become a limiting factor. At the end of the dosing period (a week, typically) we perform a 50% water change. This effectively removes 50% of the excess nutrients. The next week, same thing - we remove 50% of the excess from that week, plus 50% of 50% (25%) of excess from the previous week, and so on.

Let's say your plant uptake is 1 unit per week. You dose 2 units and you flush 50% of the water. You end up with 0.5 units. Next week you dose 2 units again. You now have 2.5 units and the plants uptake 1. The excess is now 1.5. Flush half the water and you now have 0.75 units remaining after week two.

This is just an example, your dosage, uptake and water change may vary but the principle is the same. EI accumulates excess nutrients over time, until you perform 100% water change or dose the same amounts that your plant uptake.

Does that make sense now? Over time, you need to adjust your dosage to match plant uptake or perform bigger water changes to mitigate that accumulation.

[edit] head over to our helpful plant ref. thread, then to EI light article from Tom Barr. 4th paragraph: "50% weekly will keep the maximum possible build up to 2x the amount dosed for the week. So if you dosed 10 ppm of NO3, the most it would ever climb to is 20ppm as long as you did 50% weekly and no uptake took place. If you did a 90 % water change weekly, then the most it would build up would be about 12ppm. More work and effort to do the 90 % vs 50, but you get much smaller ranges, if you chose 25$, now you are at about 40ppm, so the difference in the % water changes can be used to change the build up and accumulation."

My question was: do you find it easier to dose less and adjust up until there is no deficiencies, or to dose more and adjust down until deficiencies become apparent then add a bit more to reach party?

[exv152]

My question was: do you find it easier to dose less and adjust up until there is no deficiencies, or to dose more and adjust down until deficiencies become apparent then add a bit more to reach party?

I find it easier to overdose ferts, and ensure I have the proper lighting intensity (med to high). Because if there are any signs of deficiencies in plants, 9 times out of 10 it's due to improper co2 diffusion. Kind of narrows it down for me.

[charlie]

I asked  on Barreport about the effects of the rumored time bomb of EI
Here is the answers in the thread.
http://www.barrreport.com/showthread.php/4882-Confusion-about-EI-and-other-myths?p=115417#post115417
Regards

[pm]

My question was: do you find it easier to dose less and adjust up until there is no deficiencies, or to dose more and adjust down until deficiencies become apparent then add a bit more to reach party?

I started with full-on EI, but have since adjusted it down, slowly over time, and watched the impact.  I mainly did this because I was finding that my plant uptake was way less than what I was dosing, and wanted to prolong my water changes (to 50% every two weeks).  I remember Tom Barr commenting on this on TPT.  I will try to find the link.

[exv152]

The other risk with just providing barely enough ferts is the fact that you're not accounting for different uptake rates of different plant species. Some may uptake more PO4, NO3 or Fe etc., compared to others, and while making some plants happy (with lowering dosing), you might actually be inadvertently depriving others. So now, you're not only struggling with ensuring proper co2 diffusion, which is a challenge unto itself, but you're also fighting micro/macro deficiencies. Then trying to find the culprit cause of your deficiency becomes an uphill battle of several things at once. That sounds more like a ticking time bomb to me, which is why I'm also a big believer in EI.

[pm]

It wasn't on TPT, but on Tom's site itself:  http://www.barrreport.com/showthread.php/11691-Hate-water-changes-EI-can-get-you-there-with-a-small-modification

This is what I am following now.

[magnosis]

great! thank you all for the valuable input. I will check on these threads later tonight and comment back.

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