Bluelab OnePen vs Combo Meter vs Combo Meter Plus: Which One Do You Actually Need
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Bluelab OnePen vs Combo Meter vs Combo Meter Plus: Which One Do You Actually Need
All three of these meters measure the same three things: pH, conductivity (EC), and temperature. That's not where the real decision lives. The actual question is whether you need a probe that can go directly into your growing medium and read the pH right at the root, or whether checking your reservoir and runoff solution is enough for how you grow. Get that answer right and the rest of this comparison is mostly about form factor and connectivity. Get it wrong and you'll either overpay for a capability you don't use or underbuy for a problem you actually have.
The 30-Second Answer
- OnePen ($236.55): compact pen-style meter, Bluetooth app connectivity, solution-only measurement. Reads your reservoir, runoff, and water source.
- Combo Meter ($258.59): the classic tabletop unit with a cable probe. Same solution-only measurement as OnePen, no app, a $22 step up.
- Combo Meter Plus ($303.82): same tabletop body, but the Leap probe has a spear tip built to go directly into soil, rockwool, or coco. No slurry needed. A $45 step up from the base Combo Meter.
- The real question: solution or medium? If you're checking a reservoir or drain-to-waste runoff, any of the three works. If you need to know what's happening at the root inside a dense medium, only the Plus does that directly.
None of these is a beginner trap or an overkill purchase by default. The right one depends on whether your grow needs root-zone readings or reservoir readings. We sell all three and will tell you honestly which one matches your setup.
What all three actually measure
Before getting into what separates them, it's worth being clear about what doesn't. Every one of these three meters reads pH, conductivity, and temperature, and every one of them does it accurately enough for cannabis cultivation. None of the three is a "better" meter in some general sense. The differences that matter are the probe design, whether that probe can go into solid growing medium or only into liquid, and whether the meter talks to an app. Pricing follows those differences, not the other way around.
OnePen: the compact, connected option
OnePen is the newest of the three in form factor, built as a single pen-style body rather than a separate meter-and-probe-on-a-cable setup. It uses a replaceable probe and connects to Bluelab's Edenic app over Bluetooth, which lets you log readings and see history rather than just reading a number off the screen and writing it down yourself. Like the base Combo Meter, OnePen measures pH, EC, and temperature in solution only, meaning your reservoir, your runoff, or your source water, not directly inside a solid growing medium. At $236.55, it's the least expensive of the three, and for a lot of hydro and drain-to-waste coco growers who are checking liquid rather than probing root zones, that's genuinely all the meter you need.
Combo Meter: the classic tabletop, no app
The base Combo Meter is the more traditional Bluelab form factor: a handheld meter body connected to a double-junction pH probe on a 6.5-foot cable, rather than a single pen. It measures the same three parameters as OnePen, in solution only, with no app or Bluetooth connectivity at all, just a backlit LCD screen and push-button operation. The conductivity and temperature functions come factory-calibrated, so you're only ever calibrating the pH side. At $258.59, it costs about $22 more than OnePen for essentially the same measurement capability in a different physical form. The honest reason to pick this over OnePen is really just preference, whether you'd rather have a probe on a cable you can dunk into a reservoir while the meter body sits on a shelf, versus a single pen you dip in and pull out.
Combo Meter Plus: the one that reads your growing medium directly
This is where the real capability jump happens. The Combo Meter Plus uses Bluelab's Leap probe, which has a spear tip built specifically to be pushed directly into soil, rockwool, coco coir, or potting mix and get a pH reading right there, without pulling a runoff sample or mixing up a slurry first. That's a genuinely different job than what OnePen or the base Combo Meter do. A reservoir or runoff reading tells you what you're feeding the plant; a direct-in-medium reading tells you what's actually happening at the root, which can drift from your feed pH in dense media, uneven watering, or a soil grow where channeling creates dry pockets a runoff sample won't catch. At $303.82, it's $45.23 more than the base Combo Meter and $67.27 more than OnePen, and that premium buys specifically the ability to probe the medium itself rather than just the liquid running through it.
Solution readings vs root-zone readings: the real decision point
The honest way to decide between these three is to be clear with yourself about what you're actually measuring today, and whether that's telling you what you need to know. If you run hydro, DWC, or drain-to-waste coco and you're checking your reservoir before it goes in and your runoff after it comes out, that's a solution measurement, and OnePen or the base Combo Meter covers it completely. The Plus's spear-tip probe doesn't add anything for that workflow, since there's no solid medium to probe directly. If you grow in soil, or you're running a denser coco or rockwool setup where you suspect the root zone might be reading differently than your runoff suggests, a direct-in-medium reading is the only way to actually confirm that, and that specifically requires the Leap probe on the Plus. Runoff pH and root-zone pH usually track closely together, but "usually" is doing real work in that sentence, and the Plus is the tool that lets you check rather than assume.
What each one actually costs, side by side
| Meter | Price | Probe | Reads inside media | App |
|---|---|---|---|---|
| OnePen | $236.55 | Replaceable pen probe | No | Yes, Bluetooth/Edenic |
| Combo Meter | $258.59 | Double-junction, cable | No | No |
| Combo Meter Plus | $303.82 | Leap, spear-tip | Yes | No |
Worth noting plainly: none of these three is a genuinely cheap entry-level meter. All three sit in the $230 to $305 range, since Bluelab builds toward accuracy and durability rather than a budget tier. If you're comparing against a $20 hardware-store pH pen, the honest answer is that these are a different category of tool, built for growers who want factory-calibrated conductivity, replaceable probes, and readings they can actually trust cycle over cycle.
Who should buy which
If you're running hydro or drain-to-waste coco and you're disciplined about checking reservoir and runoff numbers, OnePen is genuinely the smartest buy of the three, since the app logging adds real value for tracking trends over a grow cycle and you're not paying for a media probe you'd never use. If you want that same solution-only measurement without needing an app or Bluetooth in your life at all, the base Combo Meter does exactly that job for about the same money. If you grow in soil, or you're running any medium where you've had unexplained nutrient lockout or deficiency symptoms that your runoff numbers didn't predict, the Combo Meter Plus is worth the extra $45, because it's the only one of the three that can actually confirm what's happening at the root instead of just what you're feeding it.
What We'd Tell You at the Counter
If you brought us this exact question at the counter, we'd start by asking one thing: are you checking a reservoir, or are you trying to figure out what's happening inside your medium. If it's the reservoir, OnePen is the honest pick for most growers, since the app logging is genuinely useful and you're not paying for a probe you won't use. If you've had pH-related problems that your runoff readings didn't explain, or you're running soil where a slurry test is a pain, the Combo Meter Plus earns its price with the Leap probe.
None of the three is wrong to buy. The wrong purchase is the one that doesn't match how you actually grow. We sell all three and will walk through your setup with you before you decide. We don't upsell.
Shop the Bluelab meter lineup
Same three parameters, three different probes. Pick based on solution versus medium, not on price alone.
Frequently asked questions
Can OnePen or the base Combo Meter measure pH inside soil?
Not directly. Both are built to measure solution, your reservoir, runoff, or water source. To get an accurate reading inside soil or another solid medium without a slurry, you need the Leap spear-tip probe on the Combo Meter Plus.
Is the app on OnePen actually useful, or just a gimmick?
For growers who want to track pH and EC trends over a full cycle rather than just spot-checking, the logging is genuinely useful. If you don't care about historical data and just want a fast reading, it adds convenience but isn't essential.
Do I need the Combo Meter Plus if I run drain-to-waste coco?
Usually not. If you're checking runoff regularly, that's already a solution measurement that reflects what's happening in the medium closely enough for most drain-to-waste setups. The Plus matters most for soil or when runoff numbers aren't explaining symptoms you're seeing.
Why don't any of these have a genuinely cheap option?
Bluelab builds toward factory-calibrated accuracy and replaceable probes rather than a budget tier. All three sit in a similar price range because that reflects the build quality across the whole line, not because of feature gatekeeping between models.
Which Bluelab meter does Modern Farms actually recommend?
It depends on whether you're measuring solution or medium. We stock all three and will walk through your specific grow with you before you buy, rather than defaulting to the most expensive option.
Getting your meter right is only half the picture; knowing what pH range to actually target matters just as much. Our pH for cannabis guide covers targets and how to fix lockout once you've got a reading. Because, as always, we don't upsell.
For informational and educational purposes only. This article is general horticultural guidance and is not medical, legal, or regulatory advice. Cannabis cultivation laws vary by country, state and locality, and growing cannabis may be illegal where you live. Always understand and comply with the laws and regulations that apply to you before growing any cannabis plant. Product names, pricing, and specifications reflect our current catalog and are subject to change; confirm current pricing and stock before ordering.