Aqua Master Tools P50 Pro2 pH & Temperature Meter

P50 Pro2 Digital pH Meter Pen with Temperature

The Aqua Master Tools P50 Pro2 is a waterproof pH meter pen that also reads temperature. It's built for quick checks of nutrient solutions, tap water and reservoirs. This is the updated version of the P50 Pro, and the changes are practical ones: standard AAA batteries, a clearer display and a reminder when it's due for calibration.

pH decides how easily roots can take up the nutrients in your feed. If the solution drifts outside the range your feed is designed for, some nutrients become harder to absorb, even though they're in the tank. A reading before every feed tells you whether to adjust, so you're not guessing.

Most hydroponic and coco feeds are designed to run between pH 5.5 and 6.5, and soil feeds a little higher. The P50 Pro2 reads 0.0 to 14.0 pH to ±0.1, which is the accuracy you need to stay inside that window.

Temperature changes how pH behaves in water, so a reading taken in a cold tank can mislead you. Automatic temperature compensation corrects for this between 0 and 50°C. The temperature reading also tells you whether your solution is running too warm or too cold.

You can set the display to one or two decimal places. The second decimal shows small movements between readings, but accuracy is still ±0.1 pH, so treat it as a trend rather than extra precision.

It measures pH and temperature only. If you also want to check how strong your feed is, the P110 Pro2 Combo Pen reads pH, EC and temperature in one. If nutrient strength is all you need, the E50 Pro2 is the better fit.

• Two-point automatic calibration at pH 7.00 and 4.01: the meter recognises the solution and sets itself
• Calibration reminder: an icon appears 30 days after your last calibration, so accuracy doesn't drift unnoticed
• IP67 waterproof and floats: if it goes in the tank, you can lift it straight back out
• High-contrast display: white characters on a black screen, easy to read in a dim grow room or greenhouse
• Runs on 2 x AAA batteries: easier to find than the button cells the previous model used, and a battery indicator warns you before low power affects readings
• Replaceable electrode: when the sensor wears out, you replace the electrode rather than the whole meter
• Auto power-off after 8 minutes to save battery
• One-year warranty on the meter and six months on the electrode, from Aqua Master Tools, the Dutch brand that designs and builds its meters in-house

You get

• 1 x P50 Pro2 pH and temperature meter with protective cap and cap cord
• 2 x AAA batteries
• User manual

Getting it ready, and keeping it accurate

A pH electrode is a glass bulb that has to stay wet to work. If it dries out, readings slow down, drift and eventually stop calibrating. Most pH pen problems come from storage, not faults, so these steps matter.

1. Before first use, soak the electrode in tap water for at least 12 hours. White salt crystals around the tip are normal and dissolve as it soaks.
2. Calibrate with pH 7.00 solution first, then pH 4.01. Rinse the tip in tap water between the two.
3. Rinse the electrode after each reading.
4. Store it upright with a few drops of KCl storage solution in the cap. Never store it dry, or in RO or distilled water, which draws the electrolyte out of the bulb.
5. Recalibrate when the reminder icon appears, or sooner if you use the meter daily.

Tip: add a bottle of KCl storage solution to your order. A few drops in the cap after each use is the simplest way to keep the electrode accurate for longer.

When to replace the electrode

A worn electrode responds slowly, won't hold a calibration or gives a different reading each time. Clean it and recalibrate first. If that doesn't fix it, a new electrode for the P50 Pro2 brings the meter back to full accuracy for far less than a new meter. The same electrode fits the original P50 Pro.

Order online for delivery in plain, unbranded packaging, or use free Click & Collect from your local GroWell shop. If you're not sure which meter suits your setup, call or message the team and we'll talk it through.