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Thread: Control of KH and pH simultaneously with KH director, Calcium Reactor and Kalkwasser

  1. #1
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    Default Control of KH and pH simultaneously with KH director, Calcium Reactor and Kalkwasser


    I am trying to use the controller with KH director to control KH and pH, using both KH director, calcium reactor and kalk reactor. This is how it works:

    I am using the calcium reactor, connected to a socket in an ON-OFF mode. When KH is below KHnominal the socket is ON. Then Calcium Reactor is working and KH increases.

    As the reactor is quite efficient in dissolving CO2 in the media, the aquarium pH tends to run a bit low (around 7,8-8,0)

    I use the kalkwaaser reactor to increase the PH. I have two electrovalves that are activated either to send the RO water directly to the sump, or through the kalk reactor (only when pH is below 8,2 and level sensor is ON).

    The issue is that Kalkwasser also increase the aquarium KH value over KHnominal. Then I set up a program logic in the kalkwasser electrovalve socket that send the RO through the Kak recator, but only when KH value is below KHnominal and pH is below 8,2

    But since KH nominal is the same for Calcium Reactor socked and kalkwasser socket, the kalkwasser electrovalve never switches on when the KH value is above or equal to nominal (so no possibility to increase pH)

    The question is:

    Is it possible to set up a logical function to use a different KH value to control the socket of the calcium reactor and at the electrovalve socket?. For example KH1reference=7,5 and KH2reference=8,5?


  2. #2
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    In summary, you would like to have the equivalent of the virtual probe function for the KHD.
    Unfortunately, this is not currently possible.
    I invite you to make your need known by submitting it to

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  3. #3
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    First, directly answering to your question, if you want to have diffrent nominal value for same measurment parameter, Gael is right: you need to do a virtual probe copy of Kh but this is not feasible as of now.
    Now, ased on my experience,even if you had the virtual probe of kH possibility, there is a lot of chance what you want to do will not be efficient:
    I'm missing some inputs on your case so my answer can be not adapted to your case.
    So first, my questions:
    - What is your daily kh consumption? Means, if you do not add any kh (cut Klkwasser reactor and Calcium reactor), what is the daily decrease of kh of your tank?
    - What is your kalkwasser reactor and how do you using it: standard way means :
    Are you using limewater (translucent part is injected in aquiarium)?
    Or are you using the milky part(whitewash)?

    - what is the natural pH of the bac: max and min ? when you do not add anything to the tank?
    - how often you measure the kh of your aquarium daily?
    Depending on your answers:
    Kh Consumption: if your daily kh Consumption is low (less than 1° kh per day), you don't have so much "kh credit" to use to influence the pH.
    pH: need to know how much your pH need to be boosted or not. Naturally good condition istank where ph is at lowest, at least at 8.
    If you are using the standard way (limewatter) as Calcium hydroxide is not very soluble in RO water, so you will not be able to bring a lot of Kh and you will not also have a remarkable effect on the pH.

    If I were you, I would (i suppose you are using limewater):
    1- started by putting off the calcium reactor,
    2- measure Kh of the aquarium.
    3- Put in place all osmolation going thru kalwasser reactor.
    4- register pH and Kh evolution.

    If Kh is stable after two days, it means that compensating 100% of your evaporation with limewater, is equal to your kh consumption.
    If Kh had decreased, it means that kalkwasser reactor used this way can not recover your kh need.
    If Kh had increased, it means that you can not do 100% evaporation compensation thru Kalkwasser reactor.

    Then you have also to observe your ph during these days. To see if pH goes two high, was ok? or remains too low?

    Please answer my questions and I'll try to guide you as much as I can.

  4. #4
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    Hi, thanks both for your answers.

    It is new tank, so not a big coral population for the moment. I am using the limewater solution and it is able to match the daily alkalinity consumption without the need of the calcium reactor. Just setting up the system to be ready for the future.

    Let me understand the issues with the proposed configuration (in case that there is availability of KH virtual probe)


  5. #5
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    I understood your goal is to use more Calcium reactor when PH is ok and use more Kalkwasser reactor when your ph is low.
    I think using Calcium reactor in on/off mode is not good idea because it's too ON/Off and not enough flexible.
    You didn't answer number of time you will test daily the kh?
    If it's twice or three times per day, you will stay 12 hours or 8 hours with last measured kh. so your Kh can go two low or two high when you will have a high kh consumption.
    It's why GHL propose a calcium reactor mode in the kh director control panel. To act proportionnaly on your nominal value of Ph inside the calcium reactor.
    perhaps here, a valid request would be to having the capability of using Calcium reactor mode for kh on one pH probe and acting on another pH probe in KLalkwasser mode. to be able to react on both proportioannaly.

    And last remark: as you are using kalkwasser in limewater mode, I suggest you to use it in 100% case of your evaporation compensation to use it at max. And the remaining need of kh of the tank, can be answered with your Calcium reactor in proportional mode.
    By this way no need to having any evolution.
    And continue to use your electrovalve as security to do not go thru kalkwasser when the pH is too high.

  6. #6
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    In my uinderstanding, you cannot, shoud not perform on-off control Calcium Reactor (CRX) and Kalk Reactor (KalkX) for the tank pH and/or alkalinity at same time. As the parameters are closely connected together as you wrote. Especially because the KHD is not a real-time measurement but is batch measurement. If you do, you would have some swing or serious over and under shooting of alkalinity.
    I would recommend this way to maintin the stable alkalinity and to improve the tank pH.
    You set your KHD to the mode of control CRX chamber pH. This will maintain stable alkalinity. Then measure the average alkalinity supply by measuring the effluent alkalinity of you CRX by Hanna checker etc. The daily alkalinity demand of your tank can be calculated as follows.

    Tank volume 600L, Tk Alkalinity 135ppm, CRX eff Alkalinity 400ppm
    Daily Alkalynity Demand (ppm) = (CRX effluent Alkalinity - Thank Alkalinity) * CRX Flowrate (ml/min.)/1000(L) *60(min.) * 24(hrs) / 600(Tk Vol L) =
    Daily Alkalynity Demand (ppm) = (400-135)*40(ml/m)/1000(unit L)*60(m)*24(hr)/600(Tk Vol L) = 25.44(ppm -> 1.43 dKH
    I'd recommend you'd run the KalkX during night time (14 hrs) where pH goes down to supply alkalinity of about 12ppm. (night time less demand)
    Then go to the following page to get some data of Kalkwasser dosing amount.

    About 2.5ml/min. of saturated solution @25'C of kalkwasser will supply 12.9ppm alkalinity for 14 hours.
    During the day time for 10 hours, turn off the KalkX and turn on the CRXto supply balance 12.54 ppm of alkalinity.
    As per actrual alkalinity level measured by your KHD, KHD will rise or lower the pH setting of the CRX chamber to maintain stable alakalinity.
    2.5ml/min is about 30 drops per min, at the vertical end of a 1/4" tubing.

    American aquachemist Rany Holms wrote as follows according to his experiments.
    "Dosing 1.25% of saturated kalkwasser solution instantly increases 0.66 pH unit of tank water."

    The dosing amount calculated above is about 30% of 1.25% of tank volume, so we can expect 0.2 pH increase.
    But as the amount is dosed slowly during 14 houirs, it prevent system pH from dropping about 0.2 unit.
    This amount is far less then the evaporated water during the 14 hours. So leave the ATO as he works.

    I'm also running sodalime CO2 scrubber connected to the skimmer air intake and vent holes as a closed-loop.
    During the cold winter time (less ventilation), tank pH was 7.7 ~8.1, after installing Sodalime CO2 scrubber pH was 7.9~8.3.
    After adding a KalkX over the CO2 scrubber pH is about 8.1~8.4/8.5.
    By my experiments, more KalkX flow rate did not improve the pH swing range much, but only it shifts upward, but alkalinity swing range was increased.
    This could be a reference.

    Good Luck~!
    Son in Seoul
    Last edited by otimer; 10.04.2023 at 16:25.

  7. #7
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    Sorry for my english.I am new with GHL.
    My question is-is it possible to feed calcium reactor with maxi doser 2.2 on continuous dose?
    Will my kh director with SA doser 2.1 adjust continuous dosing acording to kh readings?

  8. #8
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    Hi Giedrius,

    Yes, you can use the 2.2 Maxi on continuous mode to feed a calcium reactor.

    The KH Director can auto-adjust any existing dose schedule from a Doser 2.1. It cannot however, auto-adjust if the same pump head will be on continuous mode. This is not recommended as corals do not consume an equal amount of KH on an hourly basis.
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    Please send PMs to the moderators only if you have general problems with using the forum! Thanks for helping us to keep the support efficient.

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