Aqua Master S300 Pro 2 Substrate pH & Temp Meter (Perfect for Soil!)

What does the Aqua Master S300 Pro 2 measure?

The S300 Pro 2 measures pH and temperature in substrates and liquids. It does not measure EC or PPM—use a separate EC meter for nutrient strength testing.

What types of media can I use the Aqua Master S300 Pro 2 in?

It works in moist substrates like soil, coco, potting mix, and rockwool, as well as in liquids like water and nutrient solution. The media must be damp—dry material gives inaccurate results.

How should I take pH readings with the S300 Pro 2?

Insert the probe into the active root zone after watering, not just the surface. Take 2–3 readings per pot to understand root-zone trends. It complements—but doesn’t replace—runoff pH testing.

How accurate is the Aqua Master S300 Pro 2?

It reads pH from 0.0 to 14.0 with ±0.1 accuracy, and temperature from 0°C to 50°C with ±0.5°C accuracy. It also includes automatic temperature compensation to help stabilise pH readings.

How do I calibrate the Aqua Master S300 Pro 2?

Use pH 7.0 first, then pH 4.0 for a 2-point calibration. Always pour buffer into a clean cup—don’t dip into bottles. Replace used solution after calibrating. Monthly calibration is recommended, or more often in organic systems.

When does the S300 Pro 2 need recalibration?

If readings drift, seem off, take too long to stabilise, or fail a check in fresh buffer, it's time to calibrate. Two-point calibration gives the best accuracy across the grow range.

Is the probe on the Aqua Master S300 Pro 2 replaceable?

Yes—the pH probe is replaceable and connects via a cable for easy reach into pots or tanks. Replace it if calibration fails repeatedly, readings drift, or response is slow even after cleaning.

How do I clean and store the Aqua Master S300 Pro 2 probe?

Rinse after use, clean with pH probe cleaner if dirty, and always store the tip wet in KCl storage solution. Never store dry or in plain water—this shortens probe life and ruins accuracy.

Can I use the Aqua Master S300 Pro 2 in organic or coco grows?

Yes—it’s ideal for coco and organic soil. Just note that organics can foul the probe faster, so clean and calibrate more frequently than with hydro or inert media.

Why is my S300 Pro 2 reading slow or unstable?

Common causes include dry media, salt buildup, biofilm, contaminated buffer solution, low battery, or an aging probe. Clean, calibrate, and rehydrate before assuming the meter is faulty.

Is the Aqua Master S300 Pro 2 waterproof?

The meter is IP65-rated (resists water jets and dust), and the electrode is IP67-rated (can handle brief immersion). It's built for grow-room conditions but not for constant submersion.

Can I leave the S300 Pro 2 in a tank full-time?

No—it’s a handheld tester, not a permanent in-line monitor. You can use it for regular dunk testing, but constant soaking will shorten its lifespan.

Does the Aqua Master S300 Pro 2 have a HOLD function?

Yes—it has a HOLD feature that freezes the current reading, making it easier to pull out the probe and read the screen clearly.

What batteries does the Aqua Master S300 Pro 2 use?

It comes with batteries installed. If the screen dims or readings seem unstable, replacing the batteries and recalibrating is a smart first move.

Why choose the S300 Pro 2 over cheaper soil pH testers?

Unlike cheap two-prong gadgets, the S300 Pro 2 uses a real probe with calibration, replaceable parts, and accurate readings. It’s a pro-grade tool built for growers who need reliable root-zone data.