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Confusion about EI and other myths

Discussion in 'Estimative Index' started by Tom Barr, Oct 21, 2008.

  1. Tom Barr

    Tom Barr Founder
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    BTW, the ppb meter is 7000$.
    Be nice to answer some low non CO2 questions, leaf differences in CO2 drop with light intensity etc.
     
  2. yme

    yme Lifetime Charter Member
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    hmmm......

    still difficult.....

    isn't it easier to use a small aquarium or big bucket and fill it with an exact amount of osmosis water. add then the desired amount of carbonates (e.g. KH4).

    reconnect the pH-controller and CO2 supply from "your" tank to this "test-aquarium".
    and add a powerhead for some flow.

    then you can play ! :cool:


    greets,

    yme

    btw: if the readings or not correct, should I adjust the slope at 30 ppm CO2 or 60 ppm CO2. I guess that since I am more in the 60 ppm range I should go for the 60 ppm....?
     
  3. Tom Barr

    Tom Barr Founder
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    Pretty much but since it is not sealed, the degassing occurs and there is a delay.
    This can throw off the reading.

    Best to use a sealed system and withdraw a sample from a location of interest in the tank, then allow it to equilibrate in the sealed system over time, then take a precise measurement.
    This way there's no change in the gas content of the water.


    You can adjust the slope at 50, 30, 60ppm etc.
    It's arbitrary, but I like to check at 3 , 30, and 60ppm, or close, since these are the main ranges of interest.
     
  4. charlie

    charlie Guru Class Expert

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    Guys there is some speculation out there that EI is a ticking time bomb due to it`s overdosing & the water changes not efficient in reducing that build up.
    please not this is not my understanding as I use & have been using the EI method for the longest time without issues, but I posted this concern expressed by some members of my local club & was pretty sure that subject was addressed here on this forum, so if anyone can point me to it , I would be happy to direct my fellow local hobbyist to it.
    Regards
     
  5. Gerryd

    Gerryd Plant Guru Team
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    The EI sticky should cover this. If not, have them simply READ THIS THREAD :)

    What are the 'concerns' folks have?

    Doesn't matter for the following reason:

    There are MANY examples of folks using VERY HIGH ppm levels (like myself) and yet fish, shrimp, and plants are all 'fine' with no issues. This FALSIFIES the myth that high nutrients are an issue.

    How can the recommended 50% water change NOT dilute the buildup?

    I do not ask these questions of YOU, but to those in your club.

    They are merely succumbing to fear IMO, and clinging to old/comfortable info regardless of correct or not....Is too bad...
     
  6. Tom Barr

    Tom Barr Founder
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    Simple

    Math does not lie.

    If you assume you dose say 20 ppm NO3 per week, total, and you do a 50% water change, there's no possible way to get more than 40 ppm without adding other sources of NO3.
    This assumes that there is absolutely NO plant uptake of the NO3 also.

    This type of math is fairly basic, it's called infinite series. High school math, perhaps they slept through it?
    The old post from the APD, not myself, illustrated this 2 decades ago, it's still up on theKrib.com:
    Link

    http://www.thekrib.com/Plants/Fertilizer/pmdd-tim.html

    I just extended the water changes to 50% weekly is all.
    Many discus keepers do 2x a week, 30-50% anyway.
    Then I have a good estimation of the MAXIMUM possible ppm build up.
    Or a worse case scenario.


    Text:

    Figuring the cumulative change in aquarium concentration of Fe (or any element) in PPM after long term daily PMDD use with periodic water changes

    The tricky part about this is knowing depletion rates. I can figure out how water changes will deplete an element, but I don't know how much plants will. Well, since my intent is to avoid overdosing Fe, I'll look at the worst case: one where no Fe is used by the plants (sure, a rotten assumption since the whole point is to provide Fe, but it does yield an upper bound or maximum possible concentration).

    Turns out concentration buildup given periodic water changes is one of those Geometric Series things.

    Say "D" is the total concentration increase after multiple PMDD doses preceding a water change (figured in mG/ltr per part 1). Say "R" is the portion of pre-change concentration that remains after the water change (ie a 25% water change leaves 75% of concentration).

    Well, after 6 weeks, you'd have a cumulative concentration of:

    (((((D*R)+D)*R+D)*R+D)*R+D)*R+D or
    D*R^5+D*R^4+D*R^3+D*R^2+D*R+D or
    SUM n=0 to 5 of (R^n+D)
    Now, over many many weeks you'd have a cumulative concentration of;

    SUM n=0 to infinity of (R^n+D) or
    D/(1+R) Simple result, aye?
    So, using this secret formula D/(1+R) and putting it in terms of daily doses, days till water change, and % water change (note: % water change = (1+R)):

    Long Term Cumulative Increase in Concentration =
    (daily increase from dose)*(doses till change)/(% water change)
    in mG/ltr or PPM in days in decimal
    only valid if water volume
    change >> dose volume
    Carrying over the example from part 1): 1.66 ml PMDD dose daily, but with 25% weekly water changes;

    (0.0144 mG/ltr Fe)*(7)/(0.25) =

    _0.4mG/ltr Fe_ final aquarium concentration
    Uh-oh, 4 times too high! That's why I ended up leveling off at a lower PMDD dose, about 1/2 ml a day, for my 45 gallon tank.

    Again, this all assumes no depletion, a lousy assumption, so I'd measure Fe as you go. As I said, this calculation is only good for an "upper bound".






    Now, if they cannot understand math and logic, but they want to argue basics on said math and logic, well, they have some issues with reality and belief, not facts.
    You cannot convince someone unwilling to suspend their belief with facts.

    This might sound harsh, but it should be. Note, this is not my personal support for the argument. This is well founded and well understood by anyone with common sense that came LONG before me that was certainly much smarter and more clever than I.
    Even if I do not know math, history, or any logical basis there............ I know fish, plants, algae etc, and I know how to test and isolate things pretty well, so I can test this and see. So can many others and they have for a good 15 years now.
    Maybe we all are just very very very lucky?

    hehe, no, not likely.
     
  7. charlie

    charlie Guru Class Expert

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    Thanks I will link this thread.
    Regards
     
  8. Tom Barr

    Tom Barr Founder
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    Actually, link the PMDD thread instead, since this is where I got it from.
    And yes, I totally forgot my high school math, but I used enough logic to know that there are partial dilutions on the remaining tank water after each water change.
    Some seem to imply that is NOT the case, which measn in fish only tanks where you feed fish food, the partial water changes will never stop the build up and increase of NH4/NO3, which is hogwash.

    Most will agree that is hogwash, but.....when they dose KNO3.......suddenly there's now a double standard and that same logic does not apply?
    You are still adding N in both cases and you still have the same dilution series in both cases.

    50% weekly water changes just made the math SIMPLE. It states that your build up will/cannot exceed 2x the weekly dosing rate.
    So if you dose 20 ppm a week of fish food or KNO3, the max build up possible is 40 ppm from that source.

    You can change the volume of replacement, say 90%, then only 10% of the water is remaining.
    The dosing calculator that Wet did allows you to model those and see the predicted outcomes.

    You should link that:
    Then they can play around with various amounts and ranges they think are best and see what is needed.
    That said, you should be able to dose less and observe the plants, algae and use LESS dosing and/or fewer water changes and/or less % water changes if you start rich, then work slow and progressive down to lower ranges.

    I see no good argument to "lard it on" if you can bother to observe and slowly modify, but not doing so will do no harm.
    I do reduced dosing and water changes in some tanks.
    But I also reduce light (and eliminate CO2 in some cases), chose non demanding plants etc.

    It's not 100% ferts, that's a narrow view on a holistic picture.
     
  9. RoryQLD

    RoryQLD New Member

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    Where can i get a par meter for $149 from ??
     
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