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Dosing with K

Discussion in 'CO2 Enrichment' started by laka, Feb 10, 2007.

  1. laka

    laka Prolific Poster

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    I am setting up a 180 gallon low tec planted tank. As far as dosing goes i would like to know how do i dose K if there are already nitrates in the water from fish/bacterial load? I only intend doing 10% water changes monthly so Tom Barr's EI index goes put the window. I aim for 10ppm K.
    Also what is the dose for direct dosing into the water. A stock solution is not feasible for 150 gallons water.

    Very informative site.
    LAKA
     
  2. Tom Barr

    Tom Barr Founder
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    Well, it's going to tough to make any predictive estimation with K+ with such low frequency water changes.

    You can buy a relatively inaccurate turbitric Lamotte or Hach Test kit, but it'll give you about a + or - range of 10ppm in that 10-20ppm range:)

    So it's not much use.

    Another method is to dose based on the N uptake, but that assumes you know what you add there fairly well also. Fish waste often gets consumed as fast it's produced in aquariums. Those feces drop intop the substrate and very slowly release the NH4/NO3. Generally at ranges that exceed the test kits you might have.
    Same with the PO4 from fish waste..
    you can try and weigh and measure the fish food before you add it, get an idea of the N/P/K content.

    Given your constraints, there's not much you are going to be able to do here.
    Just eye ball as best you can.

    Note, when you start adding more K+, the NO3/PO4 and CO2 demand will also go up as well.

    That can lead to other issues more serious than low K+.

    Just warning you.

    I'd add 1/4 teaspoon K2SO4, 2x a week, buy a Lamotte test kit, make sure the K+ does not get much over 40-50ppm.

    Realize that other nutrients will be uptaken faster now that this is not as limiting.

    Regards,
    Tom Barr
     
  3. laka

    laka Prolific Poster

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    Thanks for the advice Tom.
    According to the "Fertilator" i will need 2.5 teaspoons in a water column of 150 gallons to get potassium redings of 10 ppm.
    What i intend doing is adding this amount initially once a month and see how things pan out. If there is no sign of K deficiency on the leaves i will keep status quo. Otherwise i may add fortnightly. It will have to be a wait and see approach.
    I have just bought a bag of KCl so i'm stuck with this for the time being.
    If i have no readings of nitrates then i will supplement K as KNO3 instead and do without KCl
    LAKA
     
  4. VaughnH

    VaughnH Lifetime Charter Member
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    When you say this will be a low tech aquarium, what do you mean? Low light? No CO2? Both? You are planning to do water changes and dosing of some fertilizers, plus a lot of testing, so what do you gain by going "low tech"?
     
  5. laka

    laka Prolific Poster

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    Low tec for me means 2 WPG lights and no exogenous CO2 source. I still feel that as my heavily planted tank matures i will require nutrient supplementation beyond what i obtain from fish food waste water and soil. The fish population will be light.
    LAKA
     
  6. VaughnH

    VaughnH Lifetime Charter Member
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    Are you planning to follow the "no CO2" method Tom describes here on one of the forums? If so, you shouldn't plan on doing any routine water changes, or at least limiting them to twice a year or so.
     
  7. laka

    laka Prolific Poster

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    That's correct. Diana Walstad replaces 40% water every 6 months or so and tops up for any evaporative loss. I decided to do 10% change monthly plus any top ups as required.
     
  8. VaughnH

    VaughnH Lifetime Charter Member
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    When you change water, unless the new water has been sitting in the open for several hours, you are introducing CO2 to the tank. This raises the level of CO2 in the tank for a short time, and that fluctuation in CO2 can trigger algae to start growing. Ten percent may be too small to do that, but why take the chance? Ten percent is also too small to do much in the way of resetting the water parameters, such as hardness, that topping off the tank for evaporation has changed. If you are still in the planning stages, and have access to a water line plus a place to drain water easily, you could set up a continuous water change system, that adds a dripping flow of water, with an overflow getting rid of the excess. That seems to work fine in my tank.
     
  9. Tom Barr

    Tom Barr Founder
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    Don't bother with the 10% at all then, follow the suggestions on the article, that will address the needs of the plants and prevent other issues from other nutrients besides K+.

    You do not need to do any changes is more the point.

    Just after a large trimminmg or if you plan on disturbing the substrate/uprooting etc.

    Otherwise, hands off.

    Do not mix the methods and do 1/2 way with the water changes, you are not preventing any significant build up etc with 10% monthly.

    So do not even bother, you don't need to anyway.
    You'll dose once a week if you follow the guideline I suggested in the article.
    That's all, and the KNO3 sounds like it will be needed, not KCL. You have no NO3 as it is.

    So adding a bit 1x a week is fine in a small amount, perhaps 2-4ppm for NO3.
    There's plenty of K+ if you do.


    You do not need 10ppm etc K+ for such a slow growing tank, the same K+ for such a tank's NO3 uptake is about .5-1.0ppm per week, not much.

    Regards,
    Tom Barr




    Regards,
    Tom Barr
     
  10. laka

    laka Prolific Poster

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    Tom
    I like the idea of low maintenance. I am more than happy to do away with water changes if averything is in homeostasis. Also if dosing wikth Kno3 will provide all the K i need oaa the merrier.

    VaughnH
    I never considered the CO2 in tap water during water changes and potential for algal growth. What puzzles me is the daily diurnal fluctuations in CO2 levels related to the normal cycle of photosynthesis. This doesn't appear to be a problem with algae. How much CO2 can 10% water change introduce into the system anyway? I suppose i could aerate the water to be on the safe side but i do not think it will be a problem.
    LAKA
     
  11. VaughnH

    VaughnH Lifetime Charter Member
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    I don't think a 10% change will introduce that much CO2 either, but it also won't do much of anything that is beneficial either. Why did you pick that number and not just eliminate water changes? You will probably add that much water to replace evaporation anyway.
     
  12. Tom Barr

    Tom Barr Founder
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    Varying the CO2 often/rapidly/up and down"confuses" the plants enzymatic machinery, and signals environmental change for algae spores.

    If the plant has low CO2 stable conditions, it will produce a lot more Rubsico to take up the CO2 that is there. It will downregulate growth and other pathways.

    A plant is large lumbering organism compared to the algae.
    It takes a while for the plant to adjust.

    That's the break the algae spores exploit, with each other and with plants which make great places to grow for them.

    If you have high CO2, why produce all this extra expensive Nitrogen rich enzymatic machinery? You do not need it, so the plant degrades it and increases other pathways to account for less demands for growth and maintenance, so it upregulates growth to match the environment.

    It has an optimal environment in both cases, but the growth rate is slowed due to low CO2.

    About 10x slower.

    And that's about what my test predicted for a non CO2 water column dosing approach when I measured the parameters.

    You can simply measure NO3 if you are concerned. A well run non CO2 planted tank will achieve balance, but that does not mean no work at all, just well managed work.

    Ideally when you measure NO3 say once a week or once a month, you should measure right before you planned on dosing and you should read 5 ppm or less, most well run non CO2 planted tanks run near 0ppm.

    They can handle low levels as the plant growth is greatly reduced by an order of magnitude. So as the fish and bacteria/dead plants leaves produce NH4/NO3, it's used up.

    So you never measure any, it's assimilated before you have a chance to measure it.

    So the tank can appear to run without any measureable NO3/NH4 at all!
    Note, many older test about growign aquatic plants suggest very low N and P levels for best growth.

    Such balanced tanks seemed to have this trait, while others that had constantly rising NO3, had algae issues(due to NH4, not so much NO3 levels).

    This explains a great many observations/correlations that folks made assumptions about in the past. These folks where smart also, but they made understandable, but wrong assumptions about the observations.

    They needed to go back and add inorganic sources of nothing but NO3, rather than organic sources of N like too many fish, too much fish food, too much garden soil that had not been boiled or soaked a few weeks prior.

    By the time they measured things, the NH4 had long since gone to NO3 and the algae was home to roost.

    The crazy thing, at least to myself, was these same folks never tested their hypothesis, they just assumed that because everyone suggested that was the right theory, it must be right.

    I mean it was very simple to add KNO3, it was very simple to add KH2PO4.
    Then observe if it induces the algae spores to bloom or not.
    You need to start with a relatively stable algae free tank and then perturb it with each variable and then both to see.

    Don't you think that is a simple thing to do if you make such a hypothesis and given the fact so many have algae and you link it to those two nutrients?
    I'm still amazed no one ever did that and some still suggest these cause algae.

    If you make a claim that high NO3 kill fish, and we should not dose KNO3 because of that, you need to show cause/correlation and test it to show support.

    I have/did and have not found any support, I've found the range to be enormous.
    Same for PO4. Same for K+. Same for Traces. Same for GH. and as long as the CO2 is stable, the same for CO2.

    Now I've added high amounts to non CO2 tanks also, I still was never able to perturb the tanks(4 of them) with KH2PO4/KNO3/Traces.

    So they appear to be as robust in response to high nutrient levels as CO2 enriched tanks. Note, they have much better stability in terms of nutrients levels also vs the CO2 enriched tanks that remove nutrients 10x faster.

    This mirrors the predictions my general theories hold for both CO2 and non CO2 methods.

    The only caveat: careful not to overdose the nutrients and have to test, you can avoid testing altogether and still dose to a slight deficiency.
    Plants take a longer time(well, 10X longer) to express a problem as they do in a CO2 enriched tank.

    So if you are running low, you can see it and catch it over a 10-20 day time frame vs a 1-2 day time frame.

    So the plants now become the test kit, or a phytometer.

    You can find out how a plant responds to low NO3 by withholding the KNO3 dosing for a little while(add K2SO4 during this time) and wait and watch. See who starts acting squirrley first, then use that weed as your test kit to know when to add more KNO3.

    Simple huh?

    Not sure why the heck these folks don't tell folks such simple methods.
    Sprinkle fish food and praying is not a good method, nor is a test kit, that just measures N it does not tell you really if the plant has enough N or not.
    A plant will not lie, a test kit and our assumptions about them most certainly can fool you.

    Regards,
    Tom Barr
     
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