Best pH Meter for Hydroponics in Australia: Pens, Probes and Calibration Solution

Chris Brubeck. Reviewed October 2026.

A pH meter is the one tool every hydroponic grower needs, and it's the one most people buy twice. The first one is usually a cheap pen that drifts within a few months and can't be fixed. This guide covers what actually matters when you buy a meter, which type suits which grow, what to do about probes, and which calibration solution to keep on the shelf.

If you already own a meter and the readings are jumping around, start with our pH meter troubleshooting guide instead. This one is about buying.

What Matters When You Buy a pH Meter

A replaceable probe. This is the big one. The glass membrane on a pH probe ages with normal use. After 12 to 18 months it responds slowly, drifts, and stops holding calibration, and no amount of cleaning brings it back. If the probe is sealed into the pen, the pen goes in the bin. If it unscrews, you replace the probe and keep the meter. Over a few years that's the difference between buying one meter and buying three.

A double-junction probe. Nutrient solution is hard on a probe's reference system. A double junction puts an extra barrier between the solution and the reference, so it fouls more slowly and lasts longer in a reservoir full of mineral salts. The PenPlus, Combo Meter and Soil pH Pen in this guide all use double-junction probes.

Automatic temperature compensation (ATC). pH readings shift with temperature. ATC corrects for it, so a 16°C winter reservoir and a 24°C summer one read true. Don't buy a meter without it.

Proper waterproofing. Meters get dropped in reservoirs. IP67 survives a dunk. IP68 is fully submersible. Splash resistant isn't enough for a grow room.

Resolution you can use. Most pens read to 0.1 pH, which is plenty for adjusting a reservoir. Reading to 0.01 helps if you're logging trends or chasing small drifts.

Easy two-point calibration. Look for pH 7.0 and 4.0 calibration that takes a minute, ideally with a reminder when it's due. A meter that's a hassle to calibrate doesn't get calibrated.

Which Type of Meter Suits Your Grow

A pH pen, if you already have an EC meter or you're just starting. The Bluelab pH PenPlus takes a replaceable double-junction probe, reads temperature, is IP68 rated and reminds you to calibrate every 30 days. It's the one we'd buy for pH alone. The Apera pH & Temperature Pen is a solid no-frills option with ATC and an IP67 body that floats if you drop it.

A combo meter, if you test pH and EC every day. Most growers check both numbers every time they look at the reservoir. The Bluelab Combo Meter reads pH, EC and temperature at once, and its pH probe is on a standard BNC fitting, so the meter outlasts the probe.

A pen for in-media pH, if you grow in coco or soil. Reservoir pH and root zone pH aren't always the same. The Bluelab Soil pH Pen reads directly in coco, soil and rockwool, so you see what the roots see without slurry testing.

A monitor, if a bad night would cost you a crop. The Bluelab Guardian Monitor WiFi sits on the wall with probes in the reservoir and sends an alert to your phone when pH, EC or temperature moves out of range. It doesn't replace a handheld for calibration checks, but it catches a 2am pump failure before morning.

Pair any pH-only meter with an EC meter. The Bluelab Digital EC Meter covers conductivity and temperature, and our EC guide covers what numbers to run.

pH Probes: When to Replace and What to Buy

A probe is a consumable, like a filter. Budget for one every year or so.

Signs a probe is finished: it won't complete calibration with fresh solution, the reading keeps drifting after a proper clean and an overnight soak in storage solution, it takes more than a minute or two to settle, or two tests of the same sample come out noticeably different. Cracked or chipped glass is an instant replacement.

For the PenPlus, the replacement is the Bluelab pH ProbePlus. It unscrews and screws in, then you calibrate and you're back in business. Check the probe fitting before buying a replacement for any other meter, since probes aren't interchangeable across models.

Two habits get you to the top of the 12 to 18 month range: rinse the probe after every reading, and keep the tip wet in storage solution between uses. Most probes that die early were left to dry out.

Calibration Solution: What You Need and How Often

Calibration solution, also called pH buffer, is a liquid held at an exact known pH. Calibrating tells the meter what its probe signal means at those known points. Without it, your meter's number is a guess.

Which values. pH 7.0 and pH 4.0. Calibrate at 7.0 first, then 4.0, unless your meter says otherwise. That pair brackets the 5.5 to 6.5 range nutrient solutions sit in. pH 10 buffer is for alkaline work and hydroponic growers don't need it.

Bottled buffer. The pH Buffer 4 & 7 bottles are the cheapest way to calibrate. Pour a little into a clean cup, calibrate, then throw that solution away. Never calibrate in the bottle and never pour used buffer back, since one contaminated pour ruins the rest of the bottle. If you'd rather not deal with bottles, the Probe Care Kit below comes with single-use sachets. Once a sachet's open, use it and bin it.

How often. Every 2 to 4 weeks for a meter in regular use, after every probe clean, after the meter's been in storage, and any time a reading looks wrong. Don't wait for the plants to tell you the meter's off.

Storage solution. This is a separate solution, usually potassium chloride (KCl), that keeps the probe hydrated between uses. It isn't for calibrating. Tap water isn't a substitute, and distilled or RO water slowly damages the probe's reference system.

One box for all of it. The Bluelab Probe Care Kit has pH 4.0, pH 7.0 and 2.77 EC calibration sachets, cleaning solution, KCl storage solution, calibration cups, a brush and a chamois. If you've just bought a meter, it's the easiest way to get everything at once.

Adjusting pH Once You Can Measure It

A meter tells you where you are. GT pH Up and pH Down move you where you need to be. Add small doses, let the reservoir circulate for 15 to 30 minutes, then test again. Chasing the number with big doses causes overshoot and a reservoir that swings all day.

If your pH won't hold once you've set it, that's a water or reservoir problem, not a meter problem. Our guides on pH that keeps rising and pH that keeps dropping cover the causes. And if the plants are showing symptoms alongside the drift, PlantMDx connects your readings to what you're seeing on the leaves. Free, no signup.

A Word on Cheap Pens

The cheap pens on marketplace sites read fine out of the box. The problem shows up a few months in. Most have a sealed single-junction probe, many have no real temperature compensation, and when the probe goes the whole pen goes. If you've got one and it's drifting, it's probably not you. It's the probe, and there's nothing to replace.

Browse the full pH and EC meters collection to compare everything side by side.

Building a complete setup? Every kit from our Grow Tent Kit Builder includes Bluelab pH and EC meters and pH 4 and 7 buffers.

Frequently Asked Questions

What's the best pH meter for hydroponics in Australia?
For pH alone, the Bluelab pH PenPlus, because the probe is replaceable and it's IP68 rated. If you test EC as well, a combo meter like the Bluelab Combo Meter saves carrying two pens. Whichever you choose, get one with a replaceable double-junction probe and automatic temperature compensation.

How long does a pH probe last?
Usually 12 to 18 months in regular hydroponic use. Keeping it wet in KCl storage solution and rinsing after every reading gets you to the top of that range. A probe that's been left dry may never fully recover.

What calibration solution do I need for a pH meter?
pH 7.0 and pH 4.0 buffer. That two-point calibration covers the range hydroponic nutrient solutions sit in. You don't need pH 10 buffer unless you're working with alkaline solutions.

Where can I buy pH calibration solution in Australia?
We stock pH Buffer 4 & 7 in bottles, and the Bluelab Probe Care Kit includes calibration sachets, shipped from Melbourne. Both work with any pH meter that calibrates at 4.0 and 7.0.

How often should I calibrate my pH meter?
Every 2 to 4 weeks in regular use, plus after cleaning the probe, after storage, and any time a reading looks off. Calibrate more often if you're making big reservoir changes.

Can I store my pH probe in water?
No. Tap water leaves deposits and distilled or RO water damages the probe's reference system over time. Use KCl storage solution, and if the probe's been sitting in water, soak it in storage solution and recalibrate before trusting it.

Is a pH pen or a combo meter better?
If you already own a good EC meter, a pH pen is all you need. If you're buying from scratch and check both numbers every day, a combo meter is quicker and means one device to calibrate and look after.