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Now about that Ca:Mg Ratio

Discussion in 'Advanced Strategies and Fertilization' started by Tom Wood, Dec 3, 2005.

  1. Tom Wood

    Tom Wood Guru Class Expert

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    Hey Tom,

    As you know I've been fighting my new water with no success. One of the things I've been concentrating on is getting the Ca:Mg ratio closer to the supposed optimum of 3:1 or 4:1. When in Austin I had no problems growing what I wanted, so I looked up their water report and discovered that the water I was using there was 1:1 Ca:Mg.

    [​IMG]

    The column labelled GWTP stands for Green Water Treatment Plant, which served my old area of town. Both Ca and Mg are at 15ppm. (By contrast, my new water has 83ppm Ca and 50ppm Mg.) I know you've been studying Ca, with Mg coming up, so I was curious as to why the 3:1 and 4:1 ratio didn't seem to matter when I was in Austin.

    I'm going to flush the tank and reconstitute the RO, one more time, to match the Austin water. Do you see anything else there that is odd?

    Thanks,

    TW

    PS: Hope you are feeling better. :D
     
  2. Tom Barr

    Tom Barr Founder
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    Re: Now about that Ca:Mg Ratio

    I doubt the Ca/Mg is the issue, rather, the KH.

    I know high levels of Ca cause no issues, but I'm not sure of 50ppm of Mg.
    I know min ranges, but max ranges I'm not ready to say much about just yet for Mg.

    I'd look at KH personally.

    Regards,
    Tom Barr
     
  3. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    I've tried it with low KH and the response is the same. The plants make a weak attempt at growing, but nowhere near the lushness I was getting in Austin. And we're talking simple stuff like h. difformis. It's like they are being held back by something.

    The Austin KH is about 4 degrees, so I'll target that along with the 15ppm Ca/Mg. (Edit: Here the tap KH is 16 degrees.)

    Thanks,

    TW
     
  4. Tom Barr

    Tom Barr Founder
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    Re: Now about that Ca:Mg Ratio

    After a week or two, things may bounce back.
    It will not immediate, high Mg may be part of it, but if you cut with RO, then the issue shoukld not be that big, 25% of 50ppm Mg is 12.5ppm, not that much and certaintly not enough to cause issues. Even 25ppm is unlikely.

    But, you can simply add Ca(NO3)2, or CaCl2, CaSO4 etc to see.
    I'd also suggest TMG and 1.5x more Traces.


    Regards,
    Tom Barr
     
  5. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    It was the Mg, not too much, too little. I was dosing based on the fertilator to get Ca at 15 and Mg at 5ppm. I used Equilibrium one time, Barr GH Builder another, reconstituting with partial tapwater another, and CaCl with Epsom salts another with no success. Always stunted slow growth. The common factor was that with each mix I always targeted 15ppm for Ca and 5ppm for Mg. Both Equilibrium and Barr GH Builder automatically set Mg to just under 5ppm if dosed to get Ca at 15ppm.

    When I threw out the ratio, and especially the 5ppm for Mg, and instead dosed both to 15ppm, the plants have grown more in two days than in two months. I don't know why the fertilator has such a low recommendation of 2-5ppm, or if the 3:1 ratio is off. But something between the two is wrong.

    TW
     
  6. Tom Barr

    Tom Barr Founder
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    Re: Now about that Ca:Mg Ratio

    Read the Calcium report coming up here(tonight or the following day depending on Greg's schedule).

    The rec for solutions is typically 1:1, but I think simply dosing more will do it.
    The GH booster has more Mg the SeaChem Eq and less K+.

    Ca is not as critical as many think, as long as there is some there. Plants seldom have issues with it. Mg perhaps, but seldom Ca.

    Mg is this month's subject.
    I'll hopefully get it around the 15th to Greg.


    Regards,
    Tom Barr
     
  7. detlef

    detlef Subscriber

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    Re: Now about that Ca:Mg Ratio

    Hi Tom Wood,

    now that you have fixed your water/growth problem by setting the Ca:Mg ratio to 1:1 (each 15ppm) I just want to know out of curiosity where your KH settled?
    Did you dose enough PO4 after the move? I recognised that back in Austin you had quite a bit of phosphates in the tap.

    Regards,
    Detlef
     
  8. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    I must have miscalculated the amount of water remaining in the tank after draining it down to a certain level, because the KH ended up higher than I wanted. It's now at 6KH when I was targeting 4KH. Although the plants have responded, the h. difformis is still not putting on the fast growth that it did in Austin. It's hard for me to believe that it's the KH though. Mexican Oak Leaf is doing well, but it's native to this part of the world.

    TBarr - earlier in this thread you said the KH might be an issue - did you mean go higher or lower?

    TW

    Edit: Yes, I've been dosing PO4 all along. And KNO3, and K2SO4, and CSM+B, and Flourish.... And feeding four growing goldfish enough to send NO3 and PO4 up anyway. If this tank were still in Austin I would have trimmed several 5 gallon buckets of plants out of it by now.
     
  9. Tom Barr

    Tom Barr Founder
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    Re: Now about that Ca:Mg Ratio

    Lower!!!!

    I think what you are seeing is more related to that, perhaps some low Mg and then the response time lag............but I think I've only rarely ever seen Mg related issues, I have to specifically induce them which is the next nuterient experiement I have planned most likely.

    By doing these in depth articles, I can get a feel for what is happening ands where we should look into the research with some test of our own to answer some potential problems/issues/questions we might have.

    Since Mg is up next, I'll have a good feel for that later this month and so will the rest of you.

    Generally, if you add more, that addresses things, the ratio should not mean much, this is a general rule.

    Higher KH, NH4 are not good things as rule. A few plants don't like higher KH, some seem to.

    But KH will cause much more plant related growth issues than GH will, GH is like any nutrient, add more. KH is not.

    I think I'll need to do a very in depth article on KH/alkalinity.


    Regards,
    Tom Barr
     
  10. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    Seems odd that h. difformis of all things would be so touchy, it's supposed to be tolerant over a very wide range of conditions. I'll drop it to 4KH and see if it helps.

    What would you suggest for GH, assuming I'll keep the 1:1 ratio for Ca and Mg?

    Yeah, I'm now very curious to see what you have to say about Ca, Mg, and KH. While this has been interesting to delve into, I'm to the point now where I just want it to work. :D

    TW
     
  11. Tom Barr

    Tom Barr Founder
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    Re: Now about that Ca:Mg Ratio

    Yes, the GH is fine at 1:1, as long as the Mg is not that high, Ca on the other hand, can be quite high.

    So there are limits to any ratio.

    Regards,
    Tom Barr
     
  12. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    Is it possible that Ca and Mg in natural waters can be somehow unavailable to plants? I swear I'm getting a better response from the plants when adding additional CaCl and Epsom salts, rather than relying on the natural tapwater.

    All the springfed waterways around here have *no* plantlife in them, and they probably have the same 83ppm Ca and 50ppm Mg that our springfed water supply has. I'm cutting that with RO to get to 15ppm Ca, and then supplementing the Mg with Epsom salts to get it back up to 15ppm as well. But it looks like additional CaCL and Epsom Salts to get both up to 20ppm+ helps.

    What does "Mg is not that high" mean then in terms of ppm?

    TW
     
  13. colonel

    colonel Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    TW I often wonder the same thing. My water out of the tap has a GH of 5.5 dh, and the water company told me that on the day I called Ca tested 26 ppm and Mg 6.1, and that those numbers are just about the usual from day to day. That being said Lately I have had what I really think you be Ca def. distorted new growth on some of my red plants, along with cupped U shaped leaves, folded leaf edges or even rolled up leaf edges on H. polysperma.
    Im sure this could also be another nutrient, but its showing up just how Ca def. is always described, and with 5.5 GH and a supposed 26 ppm Ca, makes me wonder if for some reason that Ca is unavailable also. Intresting someone else is thinking the same thing. Will be neat to see what others have to say about it.
    Matt
     
  14. reiverix

    reiverix Lifetime Members
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    Re: Now about that Ca:Mg Ratio

    I've found pond snails to be a good calcium indicator. Their shells tend to go white and brittle with a deficiency. They don't last long in my tanks without adding Ca (neither does my java fern) and I like to keep a healthy population to feed my puffers.
     
  15. Tom Barr

    Tom Barr Founder
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    Re: Now about that Ca:Mg Ratio

    If you take a Ca/Mg ratio of 1:1 and raise the Ca level to say 100ppm, see what happens:)


    Ratios give an idea of what might happen, they do not predict what will happen and the range of limitatiion the real issue.

    Also Ca deficiency issues in aquatic plants are not what are classially thought of from the list of what Ca++ in terrestrial plants.

    Do not assume all plants respond to low Ca the same way. They don't. We have no definitive proof of many plant expression to Ca linitation, nor Mg limitation.

    We are likely closer to knowing more about Mg deficicency than Ca++.
    Much further because the Ca is very very seldom limiting.

    Mg on the other hand is much more likely.

    Regards,
    Tom Barr
     
  16. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    So somewhere between 25ppm and 50ppm+ is too much Mg?

    TW
     
  17. Tom Barr

    Tom Barr Founder
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    Re: Now about that Ca:Mg Ratio

    I'm not sure how much is too much.

    I do know that too little will cause issues.
    I've tested K and NO3, NH4, O2 even, CO2 obviously, PO4, Ca to over 300ppm, who knows..........I have several so called softwater plants with the high Ca++, no issues.

    I have not specifically tested for the workable range for Mg, but 10ppm vs 25ppm should not make a difference given past usag and folk's experience.

    My feelings are that is somewhat like K+.

    But I honestly do not know what the upper limits are.

    But at some point, I'll find out.

    Regards,
    Tom Barr
     
  18. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    I'm slowly bumping GH up a small notch at a time, leaving KH at 4dKH. I notice, that when using the Fertilator, it takes about a 3:1 ratio of CaCl to MgSO4 in VOLUME of teaspoons, to add a 1:1 ratio of Ca:Mg. I wonder if that is where the 3:1 ratio thing comes from.

    The recommendation at the bottom of the Fertilator is to add Mg at 2-5ppm, and I wonder where that comes from too, because it flat didn't work for me.

    In any case I'm back on track and I really thank you for all your help. :D

    TW
     
  19. Tom Barr

    Tom Barr Founder
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    Re: Now about that Ca:Mg Ratio

    Well, I think the 2-5ppm was based on PPS and Ed's approach, hydroponics.
    I do not think he's done that much with it.

    So I think I'll look into it as Steve and I suggested about 10 years ago, talk about procrastination............!!!

    I'm not going to test upper toxic limits of Ca++, perhaps the lower limits, but the upper limits of Mg would be a good thing to look at.

    I also need to talk about mass ratio vs atomic ratios.

    Regards,
    Tom Barr
     
  20. colonel

    colonel Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    TW Im curious to know what your shooting for now as far as GH in degrees? And what ratio of Ca to Mg are you adding to get your water up there? I noticed in an earlier post you had said you have gotten more growth in 2 days than you did in 2 weeks by bumping Mg up to 15 ppm to match Ca at 15ppm. Is that still what your shooting for? and how are things growing now? Just was curious to see up to date what was going on thanks!
    Matt
     
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