GroStar GS1 pH Pen

Lab-Grade pH Readings in a Pocket-Sized Pen

A pH reading that drifts even a few tenths off can throw a whole feeding program out of the nutrient uptake range plants need, which makes meter accuracy and probe reliability worth paying attention to rather than treating a pH pen as an interchangeable commodity. The GroStar GS1 pairs a lab-grade double-junction probe with a 3-color backlit display, giving a clear, color-coded read on pH and temperature in reservoirs, runoff, or nutrient solution.

Its IP67 housing holds up to splashes and brief submersion in a working grow space, and the probe is replaceable on its own without needing to buy a new meter body when it eventually wears out.

Key Features & Benefits

• Replaceable double-junction pH probe — swaps in a new probe without replacing the whole meter when accuracy starts to drift.
• 3-color backlit display — shows pH status at a glance with a color cue, even in low grow-room light.
• IP67 waterproof housing — holds up to splashes and brief submersion during regular reservoir or runoff testing.
• Ships with calibration solutions, lanyard, and manual — ready to calibrate and start using right out of the box.
• 2-year instrument, 1-year probe warranty — instrument and probe are covered separately, matching how each component tends to wear.

Who Should Use the GS1

Growers who need a dedicated, accurate pH and temperature reading for reservoirs, runoff, or nutrient solution — without paying for EC or PPM functions they won't use — are the fit for the GS1.

About GroStar

GroStar is a pH, EC, and combo meter line manufactured by Apera Instruments, a water-quality and horticultural testing instrument maker that backs its GroStar pens with a standard two-year instrument and one-year probe warranty.

Frequently Asked Questions

How do I calibrate the GS1?

Use the included calibration solutions and the pen's built-in calibration function, typically a 2-point calibration against known pH reference values. Calibrating regularly, especially before an important reading, keeps the meter's accuracy close to its rated spec.

When should I replace the probe instead of the whole pen?

Replace just the probe once you notice slower response times or readings that won't calibrate cleanly even after cleaning, since the GS1's probe is a separate replaceable component from the meter body. That keeps the cost of maintaining accuracy lower than buying a new meter each time a probe wears out.

Is the GS1 waterproof enough for regular reservoir testing?

Yes, its IP67 housing is rated for splashes and brief submersion, which covers typical reservoir dipping and runoff testing in a working grow space. Dry off the housing after use anyway, since prolonged submersion beyond the IP67 rating isn't recommended.

Does the GS1 measure anything besides pH?

Yes, it also reads temperature alongside pH, since solution temperature affects both plant uptake and pH probe accuracy. It doesn't measure EC or PPM — growers who want both in one pen should look at the GS4 5-in-1 combo pen instead.

What's included when I buy the GS1?

It ships with calibration solutions, a lanyard, and a user manual, so it's ready to calibrate and use without a separate accessories purchase. The lanyard also makes it easy to keep the pen close at hand during a reservoir check.