Bluelab Guardian Monitor


The Bluelab Guardian Monitor continually monitors the levels of EC (strength), pH and temperature of your nutrient solution.

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Bluelab Guardian Monitor

The Bluelab Guardian Monitor continually monitors the levels of EC (strength), pH and temperature of your nutrient solution.

These key metrics are so crucial to the healthy development of your crop. With this product, you can save time on manual spot-checks by hanging the monitor in your grow room and making adjustments when necessary.

This item is ideal for use in hydroponic growing systems as it incorporates several beneficial features, including the following:

  • Bluelab is a known leader in plant nutrient management
  • Made of top-quality components which are unsurpassed in the industry
  • A simple and effective alarm system tells you of drops or spikes in levels
  • It gives you consistent and very accurate readings
  • Large and easy-to-read LED
  • Will automatically compensate for differences in temperature
  • The central unit is completely water-resistant
  • Its green LED display will not disturb your plants’ light cycles
  • It comes with the manufacturer’s 2-year guarantee

How does this monitor work?

This monitor is straightforward to use. Hydroponic growing, of course, needs the careful monitoring of several key nutrient metrics. These values make the difference between a successful crop and a failure.

This product carefully monitors temperature in either Centigrade or Fahrenheit, conductivity (as measured in EC, CF, TDS or PPM), and pH levels. It does this consistently and precisely by using scientific-grade probes mounted externally. The product even provides a visual alert if any of these levels fall below, or rise above crucial pre-programmed values, because even minor issues must be dealt with before they become serious.

Many plant species bloom directly due to changes in the hours of exposure to the dark they receive. The LED display on the product glows in a plant-neutral and completely safe green colour which will not disturb the dark periods and cause any unwanted issues with your plants’ light cycles.

Any differences in the temperature of your nutrient solution may well affect pH and EC readings. Because this product incorporates a thermometer built into its conductivity probe, the data it gathers will adequately provide temperature-compensated EC and pH readings and ensure you receive the most accurate and reliable information possible.

The manufacturers have such confidence in their product’s robustness and reliability that every unit carries a two-year guarantee. The pH probe itself is the only part which is exempt from this guarantee because of the delicate workings of its glass parts, but even this comes with a manufacturer’s warranty of 6 months.

How do I use the conductivity, temperature and pH monitor?

This monitor is highly intuitive to use. Before you do anything, soak the pH probe in the KCL potassium chloride solution for about 24 hours.

Mount the product in a suitable area using the four screws supplied. Make sure to place it in an area that allows the product’s probes to reach the reservoir tank comfortably; this should be at most two meters.

You can use the two cable ties (supplied) to mount the product to a support or a hanging bar.

Avoid positioning the product in an area of direct sunlight. Though the unit is fully waterproof, you should also avoid locating it near nutrients and additives. Mineral salt deposits may be corrosive and could cause a bit of damage over a long period.

Use a suitable plug adapter to connect the power supply to the unit’s underside. Attach the product’s pH probe to the by inserting and then twisting. The temperature and conductivity probe is already in its pre-attached position. You may now switch on the monitor.

Hold the unit button for three seconds to select the preferred conductivity unit. This action will cause a move to the very next unit of measurement, and the 3 LEDs will indicate this at the right of the display. Repeat the process until you arrive at your chosen measurement unit. Repeat this process for your choice of temperature measurement in Celsius or Fahrenheit.

The conductivity and temperature probe is already factory calibrated and will only require cleaning every so often. However, the pH probe will need calibrating before you use it. To do this, add a small amount of pH 7.0 calibration solution in a small container or beaker, dip the probe’s end into the solution, and then hold down the button marked ‘pH Cal’ to the left of the pH display.

Rinse the probe’s tip and repeat the process with either pH 4.0 or 10.0 to ensure a more precise calibration.

You can place the probes into the reservoir tank and fit the provided suction cup holder to the pH probe by gently pushing it over the tip and then twisting it around the stem.

The probe will then be safely attached to the side of the reservoir tank, preventing it from damaging when the solution is stirred and on other such occasions. The conductivity and temperature probe are less delicate and may be placed directly into your nutrient solution reservoir.

The alarm function is there to warn you with a flashing LED if any levels fall below, or rise above, a determined set value. To set this alarm, you should press the alarm button until you see the display “AL H” in each of the three windows. Immediately you take your finger off this button, and you’ll notice that the highest values then recorded will be displayed in these windows. Use the buttons to select which parameters you want to adjust or regulate, and then use the up and down buttons to increase or reduce each maximum parameter value.

Always remember that you’re selecting the highest acceptable and safe value. If levels exceed this, then the alarm will begin to flash. Once you have set the high values, you should press the alarm button to move on to the low values procedure and repeat this process. Then press the alarm button once more to save the selected parameters.

Always take considerable care of the pH probe, as this product’s most delicate part. You should never allow it to dry out completely; to prevent this from happening when not in use, you should replace the product’s storage cap.



  • 1 x Bluelab Guardian unit
  • 1 x conductivity/temperature probe
  • 1 x pH probe
  • 1 x power supply unit
  • 4 x screws for mounting
  • 3 x sachets of calibration fluid
  • 2 x cable ties

Check out our range of Bluelab measuring equipment and other brand solutions on our Grow Tools and Accessories page.

Where do I buy a Bluelab Guardian Monitor?

You can buy a Bluelab Guardian Monitor conveniently from our website.

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