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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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    Re: Now about that Ca:Mg Ratio

    Hi Matt,

    The 15ppm was selected because it matched the Austin water. However, I remember times when the tank hit a "sweet spot" for reasons unknown to me, and I'm wondering if it's because of getting more Ca and Mg from water replacement due to evaporation. Right now I'm using a little Excel spreadsheet to calculate where I am based on adding equal ppm of Ca and Mg. I test for GH and then adjust the ppm entry until it matches. Here's where it is today, I may go a little higher:

    GH.gif

    Edit: I'm sorta backing into the ppm numbers now because the initial water mix was a little wonky. At water change time I'll be able to make an exact mix.
     
  2. colonel

    colonel Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    thanks TW, intresting, a little bit over my head but intresting non the less ;) Correct me if Im wrong but your cutting your tap water with RO now arnt you? So what are you starting with as far as base line, then I imange your adding the extra Ca and Mg to hit a value you have found to work out so in the end your tank is at what 8.9 GH? is that with equal parts Ca to Mg? thanks for the info
    Matt
     
  3. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    Yes, but I miscalculated at the beginning. I'd flushed my tank three times with tapwater to get back to a baseline, then estimated the amount remaining to get my KH to 4dKH, down from 16dKH, with the rest as RO. But when I did that the result was 6dKH, so something started off wrong. I dosed what I *thought* would get Mg back up to about the same as Ca, and then have dosed both the same ppm since then. So it's off right now, but probably not by that much.

    In the future I'll just use straight RO and dose to get Ca, Mg and KH where I want it. I'll put in a gallon or two of the tapwater to get the super-traces, but I won't rely on it anymore for basic chemistry, it's just too variable.

    TW
     
  4. wapfish

    wapfish Prolific Poster

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    Re: Now about that Ca:Mg Ratio

    TW - I take it your growth problems are now fixed?

    Is it fair to say that the exact source of your original problem was definitely a water source issue relating to Ca/Mg/GH/KH and was probably one or more of the following:

    1) too much Mg
    2) too high GH
    3) sub-optimal Ca/Mg ratio
    4) something "different" about tapwater Ca/Mg vs exogenously added Ca/Mg (actually, it sounded more like something in the tapwater was preventing proper utilization of Ca/Mg and that you got rid of it by going to RO)
    5) KH issues with respect to any of the above

    Phew! Lots of variables.

    I can't help but wonder how far off the sweet spot for optimal growth I might personally be with params of 56/28 ppm Ca/Mg, 7-8 KDh in my tap (good ol' California hard water) vs the 86/50 ppm (approx, can't remember) values of your "bad" water or the 15/15 ppm of your new "good" water.

    Any thoughts about all of this now that the dust has settled, and are you planning on doing a little further "experimenting" with your tank to get to the bottom of things? With a good baseline and the knowledge you've already got, you're in an excellent position to to do a little messing around to track down the most critical variable(s).
     
  5. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    I *think* so. I'm getting much better growth than I did before, but still not the big lush growth I had in Austin. But I've been jacking this water around so much, I think I need to just let it be for a while and let the plants catch up. Plus, we're now heading into winter and there are temperature fluctuations and maybe biological clocks coming into play that might be affecting things separately.

    Yes. :p

    Ironically, and most frustrating was actually too little Mg when I was dosing to hit 2-5ppm Mg as recommended by The Fertilator.

    I'm not prepared to say how that spot is defined. I am really curious to see what TBarr has to say about the numbers and ratios.

    I've been fighting this thing since July of this year. I *really* don't want to have to experiment any more, I'm worn out by it. :D

    At the next water change I'll go all RO with GH and KH adjusted with chemicals, rather than cutting in some tapwater. If I see an improvement then, then I'll be able to say more about it. (This 90 gallon show tank is in the living room, along with Christmas decorations now, and the family is tired of the big green trashcan full of water, and the RO water line running across the floor from the kitchen, so a water change now will have to wait.)

    Thanks,

    TW
     
  6. wapfish

    wapfish Prolific Poster

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    Re: Now about that Ca:Mg Ratio

    Sounds like you need to do some resting and catching up as well :) . Thanks for the info.
     
  7. colonel

    colonel Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    TW, I was just wondering what are you using to raise your Ca and Mg levels? and when you do water changes the amount you add is based on what, the amount of water your changing? you the amount you need to add to the entire tank volume to hit your target PPM? Im just sort of curious, I have been not messing with my doseing at all to give the plants a chance to get used to the conditions they are in, but I still have leaves coming in pale, and syptoms that look very much as Ca def. is described.... wondering if it couldnt be lack of Mg.... was thinking of possibly fooling with GH and ratios and such after they have another week or 2 to settle in to see if that makes any difference. thanks
    Matt
     
  8. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    Hey Matt,

    I'm using this calculator to determine the amounts of CaCl2 (calcium chloride) and MgSO4 (Epsom salts):

    The Fertilator

    When I start doing water changes with just RO, then I'll dose the RO water before adding it to the tank. The amount to dose will be based on the volume of RO water in the water change.

    TW

    Edit: If you want to cut your tapwater with RO, then use an easy fraction that divides the larger of Ca or Mg to the amount you want. Then use the fertilator to calculate how much of the smaller of the two to add to get that one where you want it.

    For example, if your tapwater Ca is 80ppm and Mg is 40ppm, and you want both at 20ppm, then use one gallon of tapwater for each three gallons of RO water to cut the Ca to 20ppm. Since Mg is now at 10ppm, you need to add MgSO4 to get it back up to 20ppm, based on the water volume of either the tank, if a new setup, or the water change, as part of ongoing maintenance.

    Make sense? :p
     
  9. colonel

    colonel Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    yepp yepp, thanks TW, I dont really need to go as far as adding RO water to cut my tap water.... it seems alright Ca is said to be at 26 ppm wich should be pretty good, and Mg at 6 ppm (thats what the water company had said for that day when i called). I am almost positive all other nutrients are in line where they need to be, so I have been thinking it could be possible that the plants need a little more Mg, so I was going to shoot for the 10-15 ppm range and see if that helps out at all.... I used the fertlator and to get the entire volume of 75 g. up to that range I figured I would need to add 5 t. epsom salts to get up to 14-15 ppm. and Seemed like a lot to add every water change.... but since I only change about 25-30 g. it would make sense I would only be adding about half that amount to get the fresh water added up to that concentration..... I think thats makes sense anyway....
    Matt
     
  10. Tom Wood

    Tom Wood Guru Class Expert

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    Re: Now about that Ca:Mg Ratio

    Yeah, I'd dose based on the volume of the entire tank only once, then dose based on the water change volume. It does take about three times as much Epsom salts as calcium chloride, measured by volume (teaspoons) or about four times as much measured by mass (grams) to dose the same Mg as Ca in ppm, so it seems like a lot anyway.

    TW
     
  11. banderbe

    banderbe Prolific Poster

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    Re: Now about that Ca:Mg Ratio

    Have you had a chance to investigate this?

    My water report says that the water contains 160 ppm Mg as CaCO3, which comes out to approx. 95 ppm of actual Mg.
     
  12. Tom Barr

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

    Oh that's nice a juicy.
    That would be good to compare to the high Ca levels I've had in the past.

    Now, let's see if the test kits can match that and see how well that ppm range is from the water suppy.

    Is the tap from well, lake or rivers?

    It very well might be that high GH only from Mg, no Ca, might be the issue.
    so adding Ca might help the plants.



    Regards,
    Tom Barr
     
  13. banderbe

    banderbe Prolific Poster

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    Re: Now about that Ca:Mg Ratio

    Nah my city water report also lists 260 ppm Ca as CaCO3, which is I think about 150 ppm Ca.

    As for the water source it's a good question, one I don't have the answer to.
     
  14. Tom Barr

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

    Seems folks have high Mg and Ca at the same time don't see many issues.
    I'm still not sure about high Mg alone causing issues, I never saw that when I dosed Ca/Mg together with Seahem Eq or the GH builder Greg has.

    Noter, the Eq has a very long history of use locally(10 years) in our Club, no one has noted anything negative by adding 4-5 degrees worth of SeaChem Eq.

    Regards,
    Tom Barr
     
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