This FAQ page is currently under construction and therefore does not claim to be complete. If you can’t find what you’re looking for here, please use our manifold additional support resources.

Frequently Asked Questions

Presales 17 questions
No questions matching current filter

Frequently Asked Questions

General 7 questions
  • Where do I find the newest firmware for my device?

    The newest firmware of all devices is always included in the newest version of the PC software GHL Control Center (GCC).

    The update is done through GCC, during the update process GCC finds the newest firmware for your device automatically.

    In case you need direct access to the firmware files (e.g. for an emergency update) the firmware files are located in a directory similar to this:

    C:\Program Files (x86)\GHLControlCenter_V1121\Firmware

    (beginning of the path depends on the GCC version and the install location)

  • KH Director Tips & Troubleshooting

    he KH Director (KHD) was designed for maximum accuracy and operational reliability.

    It is essential that you download and follow the latest KHD instructions in our download area.

    Hints for achieving maximum accuracy (in addition to the instructions)

    • Calibrate the associated dosing pumps as exactly as possible. More here.
    • Calibrate the pH electrode carefully and regularly. For a max. accuracy we recommend a calibration interval of max. 4 weeks.
      Then check the calibration: Immerse the electrode sequentially in the two calibration liquids (pH 4 and 7) and observe the measured pH value (visible on the KHD page in new GCC versions, if necessary, update GCC). The value should differ max. 0.1 each.
    • The shorter and the lower the height differences of the tubes involved, the better. The reagent tube should not be longer than 70cm in total (without pump).
    • To avoid bubbles in the reagent tubes, be sure to use the supplied Flex PVC tubing. You are welcome to contact us directly if you do not have it.
    • The waste water tube must not hang in the water, it must hang freely over the water surface.

    (These are partly repetitions of the manual, due to the importance and the experience that the instructions are not always fully followed, they are mentioned again)

    Possible problems and causes

    Error message “Titration takes too long”

    This message appears when the KHD failed to complete a measurement. The measurement is stopped after a certain time if the pH value could not change sufficiently.
    If this error occurs, you should watch the progress of the pH value during the measurement for further diagnosis (visible on the KHD page in new GCC versions, if necessary, update GCC). Does the pH value change? From what value to what value?

    Possible causes:

    • Reagent empty – top up and vent system
    • Internal circulation pump does not run (pump should be heared during measurement and water circulation in the measuring cell is visible after removing the housing cover) – Contact Service
    • Internal reagent tube is clogged or pinch valve is not open (can be seen after removing the housing cover) – Contact Service
    • Measuring cell is not (sufficiently) filled with sample water, as result the pH electrode is not submerged – Find and eliminate the cause
    • pH electrode defective, can be found out by calibration – Replace pH electrode

    Error message “Leakage alarm”

    The KHD has an internal (in-device) leakage sensor to shut down the system in case of water penetration for safety reasons.
    If this error occurs, the device must be unpowered immediately and must not be used. After removing the housing cover, you can determine whether there are traces of water inside the unit – contact Service

    Measurements do not meet expectations

    Although everything was done correctly and all calibrations are correct for sure, the readings of the KHD differ from your expectations.

    According to our investigations and observations of many customers, the measured values ​​of various test procedures (test kits, optometric measurements, KHD) are up to 2°dKH apart.
    These deviations are product and user dependent, not exceptional and usually no reason for a complaint.
    The KHD offers the maximum possible accuracy if the instructions and the points mentioned here have been observed.
    If one nevertheless prefers to see other values ​​- e.g. because you are used to the values ​​of a certain test kit, you have the option of trimming the values ​​displayed by the KHD in the range +/- 30% (see setting option on KHD page).

    (Please also note the detailed explanations in the manual for this topic)

  • How do I update the WiFi Module?

    Concerns GHL-devices with ESP WiFi module, such as Mitras LX 7 and ProfiLux 4

    The WiFi module has its own file system and firmware, this is independent from the device. The file system as well as the WiFi firmware can be updated via the web interface.


    • A stabile WiFi connection to the device (resp. its WiFi module) is required. We recommend a static IP address.
    • In case myGHL is used: Prior the update myGHL should be disabled temporarily to avoid interferences during the update, reboot the device after disabling.



    Open the web interface

    Attention: The browsers Edge and Safari are not recommended for the firmware update; problems with these browsers have been reported. Please use Firefox, Chrome or Internet Explorer.

    Enter the IP address of the device in the address line of your browser. Login if you are asked to, the default login is: Username admin, PW: Starfish.

    Select file

    Open the menu (Sandwich-Button), Settings->File transfers.

    If you want to update the firmware, click firmware.bin if the file system is to be updated spiffs.bin.

    You’ll find the files in the program directory of GHL Control Center and higher.

    The firmware Version 6318 is in C:\Program Files (x86)\GHLControlCenter_V1097\WiFi\Firmware\6318.

    Open the file.

    Start file upload

    Confirm following message with OK.

    The update is running now – under no circumstances interrupt it!

    After a while the update is completed. Confirm following message, the WiFi module boots now, wait until the web page is refreshed.

    The upload is done now. On the dashboard of the web interface you should see now the actual version number of the firmware resp. the file system.

    Emergency update

    Only necessary if the file system is corrupted! Otherwise do the uploads as described above!

    In case the file system is corrupted (e.g. through a failed upload attempt) the web interface will not be accessible anymore, the above procedure is not possible anymore.

    Nevertheless, with following actions an update can be forced:

    • enter http://xxx/update in the web browser (xxx stands for the IP-address of the device)
    • select file bin or spiffs.bin
    • start upload process with clicking Update
    • the update is running now – under no circumstances interrupt it!
    • the module reboots automatically and is after approx. 1 minute operational
  • How do I achieve the maximal dosing accuracy with GHL Dosers?

    In order to achieve the maximal dosing accuracy with our dosing devices we recommed:

    1. Always use the newest firmware for your device resp. the newest version of the PC software GHL Control Center. Please update to benefit from our on-going improvements. You find the newest version in our download section.
    2. Select the appropriate pump speed. The smaller the dosing amount and the higher the required precision is the slower the speed shall be. For large amounts which don’t need a very high accuracy higher speeds are appropriate.
    3. The calibration process is extremely important. Calibration has to be made in the speed in which the pump will later be operated, of course. For calibration the hoses should be as short as possible, the total length shall not exceed 60cm (2ft). The volume, which is pumped during the calibration, must be measured absolutely precisely. We recommend a letter scale or appropriate vessel with exact markings.
      Check the calibration: Dose a certain amount and check whether the expected quantity was also dosed. Repeat the calibration if the result is unacceptable. The test amount should be large enough for the pump to run for at least 1 minute.
    4. Keep all hoses as short as possible. Use the smallest possible inner diameter which just works for your application. The larger the volume inside the hose – determined by inner diameter and length – the less accurate the dosing will become.
    5. Avoid large height differences between dosing container, pumps and aquarium. The smaller the differences the more accurate the dosing will be. The dosing container shall be placed below the water level to avoid a back flow or syphon effect, the outlet hose (to the aquarium) must never hang in the water.
    6. Although the pump heads had been produced under highest quality standards with very small tolerances it can’t be guaranteed under every possible operating condition that liquids move in the hose after a certain time. Therefore it is possible that reverse valves improve the precision. But this will only work if 5.) has been followed, especially important is that the dosing container is below the water level.
    7. Bear in mind that liquids in the tube may volatilize, depending on temperature, air pressure fluctuations and last but not least on the fluid itself. Also, gases can diffuse through the tubing and create bubbles in the tubing. If you have problems with bubbles or liquid seems to return, you should change the tubing. In particular silicone tubes have a higher gas permeability.


    Bottomline – You achieve the best accuracy with:

    Slowest possible speed, very precise calibration, thin, short and gas-impermeable tubes, small height differences.

  • What is the Power Balancing Technology (PBT)?

    The newest GHL LED-lights with integrated control are using the GHL Power Balancing Technology (PBT)

    In most dimmable lamps with multiple color channels from other vendors a change in the light color is realized by reduction of the less wanted colors.

    This means that the maximum available power can only be accessed when all color channels are operated at 100%. Once a color channel is reduced, the full lighting performance can’t be used.

    PBT allows the optimal use of existing power resources: The power that is saved in reduced color channels can be assigned to other color channels. A complex microcontroller-controlled electronics determines temperatures, currents and other parameters, and ensures safe operation and long life of all the LED color channels.

    In GHL lights LEDs are generally not operated at the maximum allowed current, through the high power reserves PBT can be used optimally.

    The following simple example will illustrate this: light with 100W total output, 4 channels red, green, blue and white, each with 25W

    Normal operation, no color variation, all channels at 25W

    All channels with standard power

    In sum 100W, the maximum light output.

    Color variation without PBT: reduction of less wanted channels red and green to 10W

    Color variation without PBT

    In sum 70W, 30W (shown here in yellow) of 100W unused.

    Color variation with PBT: reduction of less wanted channels and increase of the other channels at the same time

    Color variation using PBT

    In sum 100W, the maximum possible light power can be fully used.

    The maximum possible lighting performance is mainly determined by the power supply and temperature management. It therefore makes more sense to move the existing power between the individual channels and thus be able to use the full lighting performance even with color change, instead of just reducing individual channels and not being able to use the possibe total power.

    GHL Power Balancing Technology can be found for instance in the Mitras Lightbar 2 and Mitras LX7.

  • How do I use the Seasonal Lighting Simulation?

    Mitras LX LED Luminaires and ProfiLux Aquarium Controllers (version 3, Mini, Light and Terra) are capable of simulating the seasonal cycle of sunshine duration and sun intensity

    Example for changing intensity and day duration over the year

    The Theory of Seasons

    The duration of a day (defined as the time between sunrise and sunset), night and sun intensity change depending on the season. The amount of change that occurs throughout the day depends on the latitude; the farther it is from the equator, the greater the difference between the longest and the shortest day will be.

    Examples of Day and Night Time for Different Latitudes:

    Location Latitude Longest day Shortest day
    Brasilia (Brazil) S 16° 13 h 11 h
    Frankfurt (Germany) N 50° 16 h 8 h
    Oslo (Norway) N 60° 18.5 h 5.5 h

    Summer begins on the longest day of the year. Winter begins on the shortest day of the year. When day and night are the same length (equinox), it marks the beginning of spring or autumn. The seasons are opposite in both hemispheres.

    The sun intensity will also change more the further away the latitude is from the equator.

    Important Astronomical Time Points:

      Date on Northern Hemisphere Date on Southern Hemisphere Season
    Equinox 20. March 22. September Spring starts
    Longest day 21. June 21. December Summer starts
    Equinox 22. September 20. March Autumn starts
    Shortest day 21. December 21. June Winter starts

    The date may vary by one day depending on the year.


    Simulation of the Seasonal Course

    GHL has implemented a feature which simulates the seasonal course of lighting based on the following aspects:

    • Similar to nature but still practical for artificial biotopes
    • Simple and convenient to operate
    • Flexible and customizable to suit individual needs

    The Seasonal Lighting Simulation automatically adjusts existing illumination curves by changing light intensities and times throughout the year.

    Seasonal lighting can be combined with other simulations such as thunderstorms, rainy days, moon phases, clouds, and acclimation. That means that the brightness of an illumination channel is calculated from the combination of all active simulations.


    Enabling the Simulation

    Setting the individual illumination channels
    First you set the curves for the longest and brightest day (summer start). Additionally, for each channel the checkbox “Seasonal lighting” needs to be checked so that the selected illumination channels respond to the simulation. If seasonal lighting is disabled for an illumination channel, the set lighting curve will run every day unmodified.


    • Illumination 1 from 5:00 AM to 9:00 PM
    • Maximum 100%
    • Reduction at noon
    • Simulation seasonal lighting activated

    Programming the Seasonal lighting
    Definition of Midday: The time is taken as the center, when the assigned illumination channel(s) runs are pushed together during the year. In the example above, the center of the curve is at 1:00 PM, so here also 1:00 PM should be set as “Mid-Day”.

    Definition of the duration and brightness over the year: In a table, the duration and brightness can be defined for up to 24 days a year. The duration and brightness of days that fall between the defined days are calculated automatically. This allows for a smooth transition into the simulation. The illumination curves concerned are recalculated daily, this means the illumination brightness is reduced and the duration of illumination is shortened if necessary.

    Automatic Generation of Simulation Course
    GHL Control Center offers a convenient way to automatically fill the table with the values for day, time and brightness.

    After entering:
    – Day and month of the brightest day
    – Brightness of the shortest day
    – Duration of the shortest day
    Click on “Fill table now”. The table will automatically create a course which very closely matches the natural conditions.

    Testing Simulation Course
    After the simulation course has been programmed, you can view the resulting illumination run for each illumination channel. Open the illumination channels whose simulation course you want to see (tip: In GCC you can also view several windows – as Seasonal Lighting and illumination runs – next to each other, move window for this on the register tab), then select the date for which you want to simulate. After clicking on “Simulate now” the simulated runs are represented by dashed lines in the illumination channels.

    Simultaneous display of seasonal lighting and two illumination runs, simulated course shown:

    Automatic variation of one illumination course during the year:

    February 21 April 21 June 21
    August 21 October 21 December 21


    Please use the “Seasonal Lighting” with caution. Remember that (at large) variations of illumination duration and intensity could harm corals or plants in the aquarium and the entire system could be destabilized.


    System Requirements

    The functionality described here requires the following minimum software and firmware versions:

    ProfiLux 3 N/T (eX) 6.27
    Mitras LX 6xxx 1.19
    GHL Control Center


  • What is the meaning of the blink and color codes of the GHL Logo?

    GHL Logo Status Display

    Some GHL devices have an illuminated logo which displays system information using a RGB-LED.

    Statusdisplay Expansionbox 2

    Up to 2 information can be displayed simultaneously according to the following rules:

    • the information to be displayed are selected according to their priority
    • if 2 information should be displayed, these appear alternately


    Displayed information

      Information Combinable with other information Blinking can be switched off
    Violet blinking Device booting No No
    Red/Yellow blinking Error: Problem with serial number or security key No No
    Red constant Error: Memory defective No
    Yellow constant Memory has been reset – please reactivate control by confirming on the device No
    Red blinking Alarm Yes Yes
    Yellow blinking Warning Yes Yes
    Green blinking Activity, e.g. dosing or water change Yes Yes
    White constant Configuration LAN/Wi-Fi No
    White blinking Connecting with myGHL Yes Yes
    Blue blinking Connected with myGHL Yes Yes
    Blue constant No information to display

    (the order is according to the priority)


    The user has some options to customize the display according to his wishes, he can choose among these modes:

    • Standard – up to 2 information are shown, the logo might blink for displaying a certain information.
    • Standard w/o Blinking – only one information can be displayed, the logo shows one color permanently.
    • Off – no information is displayed, the logo is not illuminated.
    • Constant Red, Green or Blue – no information is displayed, the logo is permanently illuminated with the selected color.

    In addition, the brightness of the logo illumination can be set in the range of 20% to 100% (in the “off” mode, the brightness is independent of this always 0%).


    System requirements

    The functionality described here requires the following minimum software and firmware versions:

    ProfiLux 3 N/T (eX) 6.26
    GHL Doser 2 Standalone 1.19
    GHL Doser 2 Slave 1.19
    Expansion Box 2 2.02
    GHL Control Center


Presales 17 questions
No questions matching current filter