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High PH, High KH, Low Gh

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  • High PH, High KH, Low Gh

    I'm looking for any advice anyone cane give for my particular situation.
    My ph has been running between 8.2-8.8 everyday with a relatively high KH level of 179 ppm.
    Source water has a ph of 7.4 out of the tap and 8.2 after one hour of aeration.
    I have brought the gh of the pond down too a level of 90ppm with the help of a water softener. It was normally around 250ppm.
    I'm changing roughly 5% of the water per day with 4 days on of softened water and then one day with regular tap water. All water goes through a large carbon filter.
    The pond is partially shaded with a canopy and has 10 koi with an average size of 20-21" in 4300 gallons.
    Does anyone know why the ph is swinging so much throughout the day with such a high kh level? I'm assuming the kh only protects the water from falling under 8.2.
    If I added a RO system too bring the ph down what would protect the fish from the ph swings?
    The only addititive is koi clay.....1 heaping tabespoon per day.
    Thanks in advance for any replies since "I just don't get it."
  • #2

    Rob, I understand what you're trying to accomplish, but I think you're messing up running the water through the water softener for the fish. Save it for the shower!

    The calcium you're removing from the water by reducing the GH through the softener is something the fish should have; it's also one of the stabilizing influences in pH. For experimental purposes, bypass the softener and just give them our plain ol' water as it comes from the ground. When the GH gets up more around the 150-175 range, see if you still have the pH swings. I'd rather have stable pH and higher GH than pH swings - that's hard. See if it does the trick; if not, you can always go back to using softened water.

    Lee B


    • #3

      The low GH is the reason... PH is swinging because there are no compounds to keep the PH in a certain range, only to keep the PH above 7.0 (high KH alone should keep it above 7.8). Although the GH is high enough, it might be from things that don't provide a very stable PH.

      Rather than go into details that I'm not even sure I understand, here is the proposed fix: Add Calcium Chloride to about 60ppm. You can get it from a pool supply place and/or some hardware stores.


      • #4

        You should check out the thread "is water softener safe for koi" that I posted sometimes back.

        There are a lot of info regarding water softener and Kh, Gh.

        I use a softener myself and all I can tell you is that it's not the reason your Ph swings because softener doesn't not affect your Kh level.

        Check into it carefully before doing anything prematurely.


        • #5

          Lack of calcium. It happened to me as well only much worse.


          ZNA Potomac Koi Club


          • #6

            Thanks for all of the responses.

            I checked back in my ponding archives and noticed that before the softener the swings were much more milder. So I will put it down too the lack of calcium in the water and will dilute the softened water even further in the future with my tap water. I hate too do this because with the softened water it really eased up on the algae growth. Not green water...but the kind that inhabits the sides.
            I remember the thread because I was an active participant in it. After doing some research about Kh and from the input from the above posters....just because it is high, does not mean you will not get swings. It protects you from bottoming out...but not Topping out. As I have learned.

            So now the million dollar question.
            How do you people that run low Gh and TDS prevent Ph swings? Does the entire pond need too be shaded too restrict algae growth? I think I remember Maurice saying he was having big swings in his new koi houses and was going with more shade. Don't remember what board I read it on but would love to hear others theories.
            Forever the student,


            • #7

              I have a theory that string algae consumes calcium.

              I also notice that increased throughput over my shower filter eliminated the string algae problem in my own pond. My shower filter does use 20Kg of Bacteria House media, in addition to other things (bio-balls, matala, oyster shells, even some lava rock).


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