Review: HM Digital waterproof pH meter


Editor's Picks
Practical Fishkeeping Readers' Poll 2023
Fishkeeping News Post
Readers' Poll 2023
07 August 2023
Fishkeeping News Post
Countdown for Finest Fest 2023
20 April 2023
Fishkeeping News Post
Pacific Garbage Patch becomes its own ecosystem
20 April 2023
Fishkeeping News Post
Newly described snails may already be extinct
20 April 2023

A snazzy little device, this waterproof probe takes the fear out of dropping expensive gadgets into the aquarium to the detriment of both livestock and my wallet, writes Nathan Hill. It even floats and doesn't create an owner's wet arm on retrieval...

As for performance this PH-200 unit tests a range of anywhere between 0 and 14 on the pH scale and goes down to two decimal places with an accuracy of plus or minus 0.02 on a reading. That’s none too shabby.

At extremes you can get deviation in reading and it’s worth recalibrating the device to pH 4.0 or 10 in accordance with the instructions given. For most of us fishkeepers, however, 7.0 should be just fine and dandy.

Be cautious using the unit with water in which the conductivity is incredibly low. In these instances, you’ll need to swish the probe in some higher conductivity water first before plunging. It’d be wise to do several tests here, too.

It also doubles up as a thermometer, although it’s unlikely you’ll be purchasing the unit for this single feature.

It also comes factory calibrated and, out of the box, gives a pretty good selection of readings as I plunge it into tanks, tea and any other fluids knocking about.

Like all pH probes it’ll need regular recalibration, with a monthly cycle being wise depending how much you use the thing. Planted tank keepers and marine aquarists might want to up that calibration, combined with more routine cleaning of the probes, due to residues associated with those kinds of tank.

Calibration powders are supplied, along with a lanyard and a pouch of storage solution, so there’s no excuse for letting things drift.

Essentially, the probes need to be doused with a storage solution when not in use and this is provided, along with a handy small sponge and cap, to keep the liquid where it needs to be. Both this solution and the calibration powder can be purchased separately.

As a pleasing touch, the probe end of the device can be replaced if it ever dries out, expires or becomes otherwise damaged.

Be careful when removing or connecting the probe end, however, as the pins connecting are quite fine and could be damaged.

I’d also potentially consider occasional light use of silicone lubricant on the seal rings found throughout the unit to avoid potential perishing, although this is not a manufacturer’s recommendation as far as I can make out.


This does what it should do, does it quickly and accurately — and if I drop it I don’t even get a damp sleeve. Ta da, liquid test kits…

Price: £88.00; from Trademark Aquatics.

Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.

Don't forget that PFK is now available to download on the iPad.