Why does GH/KH/PH goes up after a while? - The Planted Tank Forum
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post #1 of 18 (permalink) Old 10-12-2020, 03:30 AM Thread Starter
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Why does GH/KH/PH goes up after a while?

Hello Amazing community,

I hope I can pick somebody's brain here. I've been trying to research this on my own, but not been very successful.

TL:DR: I'm trying to figure out why is the GH/KH/PH increasing as the days go by, as I'm not seeing what could be causing this considering I top of with filtered water, and only add Macros every now and then (sometimes I even forget).

I don't know if it is the substrate, the macros, or perhaps the plants or shrimps that cause the increase and that's why I'm here, to learn from you.

The tank setup:
* 7.5 GAL
* Live plants (baby dwarf tears, xmas moss, myriophyllum mini, alternanthera, pogostemon)
* Shrimp (neocaridina)
* Substrate (Shrimp substrate from Up Aqua, which is supposed to decrease PH)
* A light base of red clay under the substrate (which I added hoping it would help some ludwigia I had to turn redder by having extra source of iron)
* Injected CO2
* One piece of driftwood

The numbers:
1. Let's take the baseline after a water change
* PH is around 7.5 to 7.8
* GH is around 6 to 7
* KH is around 5 to 7
* TDS around 150

2. I dose macros 2 to 3 times per week (alternated)
* MPK to get it to between 3ppm and 5ppm, and that usually lasts a couple of days
* Fe on alternate days to try and help improve reds in the alternanthera (but it yellows my water)

3. I top off with filtered water (Zero water, almost close to RO, water registers 0 TDS)

4. After about a week, when I measure, the numbers have risen:
* PH is around 8
* GH is around 10 to 12
* KH is around 9 to 12
* TDS around 180

Hope some of you can shed some light and help me learn and understand what could be causing this, and perhaps what can I do to keep it more stable.

Thanks in advance.
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post #2 of 18 (permalink) Old 10-12-2020, 05:14 AM
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Whatís the hardscape in the tank? How old is the setup?


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post #3 of 18 (permalink) Old 10-12-2020, 06:24 PM Thread Starter
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Quote:
Originally Posted by sudhirr View Post
Whatís the hardscape in the tank? How old is the setup?
The original substrate is from Azoo (Plant Grow Bed), trying to remember is about 2 to 3 years (I can see that the bottom quarter inch is starting to get finer.), I also have some Seiryiu Rocks to create an elevation.
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post #4 of 18 (permalink) Old 10-12-2020, 06:32 PM
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Originally Posted by Alphazygma View Post
I also have some Seiryiu Rocks to create an elevation.
Seiryu rocks will make these readings go up!

Josh
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post #5 of 18 (permalink) Old 10-12-2020, 07:07 PM
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I have no experience with Seiryu stones, just a lot of reading from here in the forum. I second what @Tuister said.

https://www.plantedtank.net/forums/1...-hardness.html


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7.5 Cube - shrimp tank
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post #6 of 18 (permalink) Old 10-13-2020, 01:48 AM Thread Starter
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Quote:
Originally Posted by Tuister View Post
Seiryu rocks will make these readings go up!
Oh, thanks for the info; reading more on Seiryu stones, in conjunction with the earlier comments, I started my first tank about 6 to 7 years ago, so, those stones have been under water for quite longer that the last tank setup.

So, It does sound plausible that the rocks are degrading faster (considering that I also inject CO2)

Do you guys think that re-treating them with Muriatic Acid will help prolong how slow they release their calcium carbonate?
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post #7 of 18 (permalink) Old 10-13-2020, 04:32 AM
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The substrate could have been masking the effects of kh incrwase from the seriyu stones, now that the buffering effect of the substrate is spent you are now able to notice the effect of the stones.


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post #8 of 18 (permalink) Old 10-13-2020, 12:39 PM
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Quote:
Originally Posted by sudhirr View Post
The substrate could have been masking the effects of kh incrwase from the seriyu stones, now that the buffering effect of the substrate is spent you are now able to notice the effect of the stones.
This exactly what happened in my main planted tank. The new Amazonia substrate soaked up the hardness from the rocks until one day, all of a sudden, it's capacity was exhausted and the GH and KH suddenly started to go up, up, up!


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post #9 of 18 (permalink) Old 10-13-2020, 03:30 PM
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Quote:
Originally Posted by Alphazygma View Post
Oh, thanks for the info; reading more on Seiryu stones, in conjunction with the earlier comments, I started my first tank about 6 to 7 years ago, so, those stones have been under water for quite longer that the last tank setup.

So, It does sound plausible that the rocks are degrading faster (considering that I also inject CO2)

Do you guys think that re-treating them with Muriatic Acid will help prolong how slow they release their calcium carbonate?
The rock is made up of carbonates and calcium (and probably some magnesium) - so any rock that you see will respond to the decrease of pH in the environment. It will actually degrade with CO2 injection ... which is fine! It will release Calcium, carbonates, and magnesium into the water - it "buffers" the water in response .

The buffering capacity of your substrate is limited -- it will not buffer to the same amount forever ... eventually it stops because. As a result, your stone (via CO2 injection) may have buffered out the tank's pH drop, and then the substrate "buffered the buffer" (oh and hundreds of other chemical pathways at the same time) -- that said, if the substrate "runs out" of buffering capacity, then your pH is going to climb (as well as your KH and GH) since you can clearly see a giant rock and you cannot clearly see the pockets of buffering in the substrate.

If you treat with muriatic acid, then you are just going to take off a layer of "rock" but all the rock below it can still be degrade! Unless it removes the top layer and reveals some inert rock below (this is not going to happen).


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post #10 of 18 (permalink) Old 10-13-2020, 07:56 PM
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I just setup a 50g with Seiyru. I too notice a gentle KH and GH climb. The strange thing is pH has stabilized and gone down a little over time after initially going up. I have a neutral substrate of Seachem Flourish Black Sand.

I think it's more complex than "Seiyru causes KH and GH to go up". There are different kinds of stone called Seiyru. One thing you can do it take a small inconspicuous piece out and place it in some white vinegar and see how much bubbling you get. The more bubbling the more it probably leaches into your water due to higher calcium and/or softer stone. Another part of the complexity is that it dissolves in weak acids, so it will dissolve more the more acidic your water is below pH 7.0.

My stone was quite fizzy and I acid washed it a long time for looks. The KH and GH rise has been slow and manageable with water changes. And I think it is slowing down a little over time, hard to tell.

I have wondered if there is a strategic way to manage it by adding KH buffer to the water to assure pH is above 7.0 as much as possible, even with CO2. Then Seiyru should dissolve more slowly and water will be more stable. Just speculation.

Here's mine with the Seiyru. I have to trim the plants back constantly to see it. All that work to get the Seiyru acid washed, chipping stones to get the rights sizes and shapes and they get completely covered in green.
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post #11 of 18 (permalink) Old 10-13-2020, 08:27 PM
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Originally Posted by ahem View Post

I have wondered if there is a strategic way to manage it by adding KH buffer to the water to assure pH is above 7.0 as much as possible, even with CO2. Then Seiyru should dissolve more slowly and water will be more stable. Just speculation.
I wouldn't add buffers or try to hit a target pH, with Seiryu and a buffering substrate its difficult, its better to use a constant CO2 rate in those situations. PH drop is dependant on kH and if you have a drifting kH you can't rely on the 1ph drop method.


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Last edited by cl3537; 10-13-2020 at 08:33 PM. Reason: ...
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post #12 of 18 (permalink) Old 10-14-2020, 01:50 AM
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I wouldn't add buffers or try to hit a target pH, with Seiryu and a buffering substrate its difficult, its better to use a constant CO2 rate in those situations. PH drop is dependant on kH and if you have a drifting kH you can't rely on the 1ph drop method.
That's the problem with Seiryu, it can cause a kH increase as the week goes on and thus you have a drifting kH. My hypothesis is that Seiryu will not dissolve, or not dissolve as much, in water that is pH 7.0 and over. So if pH is adjusted higher, the "Seiryu effect" is diminished and there is less drift. So for example, the following relationship could exist in tanks with CO2:
starting pH ending pH "Seiryu effect" kH drift (for day)
Tank #1: 7.2 6.2 +.5kH
Tank #2: 7.8 6.8 +.1kH

I'm just making up those "Seiryu effect" numbers to demonstrate the kind of relationship hypothesized to exist between the Tank #1 and #2 examples. The hypothesis is that daily kH drift would decrease with an increase in nominal pH. And therefore adding a buffer would be a way to increase nominal pH.
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post #13 of 18 (permalink) Old 10-14-2020, 06:19 PM
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Originally Posted by ahem View Post
That's the problem with Seiryu, it can cause a kH increase as the week goes on and thus you have a drifting kH. My hypothesis is that Seiryu will not dissolve, or not dissolve as much, in water that is pH 7.0 and over. So if pH is adjusted higher, the "Seiryu effect" is diminished and there is less drift. So for example, the following relationship could exist in tanks with CO2:
starting pH ending pH "Seiryu effect" kH drift (for day)
Tank #1: 7.2 6.2 +.5kH
Tank #2: 7.8 6.8 +.1kH

I'm just making up those "Seiryu effect" numbers to demonstrate the kind of relationship hypothesized to exist between the Tank #1 and #2 examples. The hypothesis is that daily kH drift would decrease with an increase in nominal pH. And therefore adding a buffer would be a way to increase nominal pH.
I'm not sure where you are going with all that, again you should not be adding any buffer to manipulate pH.
You reset kH back to the default value everytime you do a large enough water change.

A practical way to deal with the problem with or without a solenoid is to do a water change and then leave CO2 off for 24 hours.
Use the pH of tank water after 24 hours as your starting point and set CO2 so the tank stabilizes at a ~1ph drop. Then you have your flow rate locked and you won't change it throughout the week even if you see your pH raising slightly, you are still getting ~30ppm of Co2.

You can repeat this every few weeks or so just to make sure you aren't getting too much kH drift (or flow rate drift) but the point is there will be kh and ph drift but it should reset everytime you do a large enough water change and the amount of Co2 injected should be the same if you keep the flow constant.


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post #14 of 18 (permalink) Old 10-14-2020, 08:06 PM
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Crazy option, but what about adding or replacing part of the substrate with fresh substrate that will keep buffering?


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post #15 of 18 (permalink) Old 10-15-2020, 04:06 AM
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Quote:
Originally Posted by cl3537 View Post
I'm not sure where you are going with all that, again you should not be adding any buffer to manipulate pH.
You reset kH back to the default value everytime you do a large enough water change.
In the scenario I am talking about, you would not reset the kH back to default at water changes. At the water change you would add a product like Seachem Alkaline Buffer. It raises the pH and kH which prevents the Seiryu rock from dissolving into the water the column, thus preventing pH/kH drift, or at least that is the hypothesis.

The hypothesis can be tested by adding Seiryu to buckets of water of different pHs/kHs and seeing if there is a difference in pH/kH drift over time (presumably caused by Seiryu dissolving into the water column).
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