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High GH/KH = bad for growing plants?

Discussion in 'General Plant Topics' started by GillesF, Nov 6, 2012.

  1. GillesF

    GillesF Member

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    Hello

    I have noticed on several occasions on Dutch forum that a high GH/KH is considered bad for plant growth. What is this based on? Antagonism? And why would it be bad for plants?

    Cheers
    Gilles
     
  2. Hallen

    Hallen Guru Class Expert

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    As far as I know it's only certain species that actually need a low KH/GH and some do seem to benefit a little from it. I've been hearing this for quite a while aswell and in my own expirience it never really confirmed with most of the comon plant species. I don't have any scientific data to back it up tho.
     
  3. GillesF

    GillesF Member

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    Yeah, I think it was species like Tonina that were more sensitive to high GH and KH?
     
  4. Wet

    Wet Lifetime Members
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    This is by recollection, but at AGA 2010 Claus Christensen shared some numbers he collected from the wild for various plants, in natural water systems where water levels, CO2, N, P, K, Fe, KH and most everything you can imagine varied greatly across parts of the water system, including areas (tributaries, brooks, fast flowing parts, slow flowing parts, etc) where the same species grew well. This was within the context of demonstration tanks he documented over months at a time showing both rich nutrient levels (lots of growth, which he disliked) and leaner levels (less growth, which he liked). But one of the things that stood out to me was GH stayed pretty constant where living things grew in the wild. I understand enough about fish and the process of things that live in water to respect GH, but I don't understand much about such things. I am intuitively more wary about GH for my fish than for my plants.

    One of the things that talk reminded/taught me was that I should always move slowly with things I don't fully understand. While I have little qualms about moving NO3 or PO4 quickly, I will not move CO2 or dose NH3/4 or do a couple other things in a tank, based on what I've experienced/killed with tanks. My understanding of GH has me respect and would move it slowly if I decide to move GH. (I haven't wanted to move GH in years.)

    In regards to high KH, I do think something's there. I've grown Tonina, Syngonanthus, Eriocaulon, and other soft water plants in both reconstituted RO/DI and hard (both GH and KH) Los Angeles tap water, always with acidic soil. My experience in RO/DI was these plants really are not *that* hard but may be picky (Erios sending out flowers and then going south, stability being important). My experience in hard water is that new growth and not-bad crowns in Syngonathus isn't hard with good fundamentals, but that old growth needs to be hidden because it turns kind of yellow and undesirable.

    That said, it's totally possible to grow nice enough looking Syngonathus sp. in hard water. Here's examples from that tank with big water changes straight from Los Angeles tap. The plants are always a little hidden for the reasons above:
    [​IMG]
    [​IMG]
    [​IMG]

    But maybe more importantly, these soft water plants are certainly interesting and Tonina tanks are certainly cool, but they're really not caring about RO/DI or water hardness cool. A dense planting of Tonina really doesn't look as nice as a nicely trimmed bush of, say, Rotala sp. 'Green' or StarGrass in most aquascapes.

    I'm totally into the spiky Eriocaulon mid/foreground plants though. But again, not that into it to actually reacquire them after a break...
     
    #4 Wet, Nov 7, 2012
    Last edited by a moderator: Nov 7, 2012
  5. mi5haha

    mi5haha Prolific Poster

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    it depends upon how hard the water we are talking about. 24GH to 35GH hard water? or just 12GH hard water?
     
  6. GillesF

    GillesF Member

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    It went over 30 GH, then I stopped counting.
     
  7. aquabillpers

    aquabillpers Lifetime Charter Member
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    GH and KH are not a problem for most plants, unless the KH is so high that it makes the pH greater than 8.0. At that point it starts to interfere with the absorption of iron. A simple solution is to replace some of your water with distilled water.

    Bill
     
    #7 aquabillpers, Nov 7, 2012
    Last edited by a moderator: Nov 8, 2012
  8. mi5haha

    mi5haha Prolific Poster

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    You may need to lower it down to 12-15GH by any means. For small tanks, you may mix RO water.

    For bigger tanks, you may use resin (hydrogen type, not sodium type for drinking water), or using oxalic acid to treat the hard water.
     
  9. dutchy

    dutchy Plant Guru Team
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    Gilles, did you repeat the test? is there something in the tank that releases Ca? I can't think of GH's like that. If we assume a 4:1 Ca/Mg ratio the Ca. would be around 140 ppm. Did you check the level with the tap water supplier?
     
  10. GillesF

    GillesF Member

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    Dutchy, the area where I come from is known for having VERY hard tap water. It is in fact the tap water with the highest GH in Belgium :)
     
  11. Tom Barr

    Tom Barr Founder
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    My GH was 24 in Santa Barbara, no issues, the KH is the only thing that would be an issue I am aware of and have noted or could not rule out, GH can be over a VERY wide range without any issues.
     
  12. GillesF

    GillesF Member

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    Tom, could you elaborate on the KH part? What were the issues and why?
     
  13. Wet

    Wet Lifetime Members
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    Have you considered setting up a little nano (a bucket works in place of a tank to save $) and cutting 25% tap with 75% RO/DI, then seeing what you think?

    DIY CO2, no fish, a couple cf in desk lamps, and a really cheap setup can make this cost effective, minus the cost of your time.

    The total cost ($, time) may be less than the time you spend wondering, "what if," no matter the results of this experience. Your call of course. It's these kinds of experiments that answer many of my questions, as well as discussion with fellow gardeners, fwiw.
     
  14. Tom Barr

    Tom Barr Founder
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    I'm not sure why, but some species seem to grow poorly with higher KH's.
    Even with cO2 etc.

    The pH optima for the enzymes that govern uptake of nutrients, metals, CO2 perhaps, may not be optimal. While we move the pH around 1-1.4 pH units with CO2...........this is not the same as a stable non moving alkalinity/KH. That is still hard high KH no matter what we do to the pH with CO2 gas.
    Most plants are more flexible, some are not. All plants seem to do better with lower KH's IME/IMO.

    So it's the higher/harder KH's that only seem to cause issues with uptake/growth. So only higher pH/KH's seem to cause enzyme uptake issues.
    The issue seems to be a the enzyme uptake level near as I can tell/guess.

    That's where I'd look, but use KH, not pH........for our system since we move the pH all over with CO2 gas, but not KH.
     
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