ARKA myAqua TDS and EC conductivity tester, pen type or inline for reverse osmosis units
Regular price
¥2,700
Regular price
Sale price
¥2,700
Unit price
/
per
¥900 × 3 with no fees
Klarna.
The ARKA myAqua testers measure the amount of dissolved salts in the water. The TDS and EC pen checks a nutrient solution or the water in a tank within seconds; the in-line tester installs on a reverse osmosis unit and continuously displays the quality of the water produced.
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Delivery within 2 to 15 business days
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The summary
- Which tester: pen for spot measurements, inline for monitoring a reverse osmosis unit.
- The ranges: from 0 to 9,999 ppm for the pen, from 0 to 999 ppm inline.
- The accuracy: 2% on both devices.
- The reverse osmosis unit: a colour indicator for the quality of the water produced.
A figure to tell you what your water contains
The conductivity of water tells you how many salts it contains: limescale, nitrates, fertiliser, minerals. It is read as EC, in microsiemens per centimetre, or as TDS, in parts per million. In hydroponics, it shows whether the nutrient solution is too weak or too concentrated; in aquaponics, it tracks how the water becomes enriched over the weeks; downstream of a reverse osmosis unit, it confirms how well the membrane is working. The range includes two testers, depending on whether you measure occasionally or continuously. Both devices show their result on a screen, with no reagent or colour chart.
🖊️ The TDS and EC pen
The myAqua TDS/EC pen is dipped into a glass of water or straight into the tank, and shows within seconds the conductivity from 0 to 9,999 µS/cm, or the TDS from 0 to 9,999 ppm, with an accuracy of 2%. It also shows the water temperature. It runs on a supplied 3 V battery and weighs around a hundred grams. After each measurement, rinse the probe with osmosis or demineralised water, then dry it before putting the device away.
Take a crop of lettuces grown in hydroponics: the nutrient solution is prepared by adding the fertiliser to the water until the target conductivity is reached, often between 1,200 and 1,800 µS/cm for leafy vegetables. Checking every 2 or 3 days shows whether the solution is becoming more concentrated, because plants absorb proportionally more water than mineral salts, or whether it is becoming depleted. You then top up with clear water or with fertiliser, rather than replacing the whole solution. The guide to getting started with indoor hydroponics gives pH and EC benchmarks for different crops.
🔁 The online tester for reverse osmosis units
The myAqua In-Line TDS connects to the circuit of a reverse osmosis unit, such as the ARKA myAQUA compact reverse osmosis unit, thanks to its 1/4 inch quick-connect fittings, the standard diameter of reverse osmosis tubing. It measures TDS from 0 to 999 ppm, with an accuracy of 2%, and shows it on a screen backed up by a colour indicator: green from 0 to 50 ppm, blue from 51 to 300 ppm, red above that. A quick glance is therefore enough to tell whether the water produced is good-quality reverse osmosis water. Two adaptors let you install it at different points in the circuit, to compare the water going in with the water coming out.
Install the tester in-line, away from splashes
The in-line tester is not waterproof: install it away from splashes, at the side of the RO unit rather than underneath. After installation, run the RO unit for a few minutes and check for leaks at every fitting. Repeat this check after each cartridge change, since the fittings will have been handled.
TDS and EC pen
The pen measures on demand, from 0 to 9,999 ppm.
Inline TDS
The in-line tester measures continuously on the reverse osmosis unit, from 0 to 999 ppm.
Green
The green indicator signals good-quality osmosis water, from 0 to 50 ppm.
Red
The red indicator light, above 300 ppm, signals a membrane that needs checking.
The in-line tester runs on a supplied CR2450 button cell, with very low standby consumption. A value that rises slowly from one month to the next signals wear of the membrane or pre-filters: you replace the cartridge at the right time, neither too early nor too late.
For a reliable measurement, leave the probe in the water for a few seconds until the reading stabilises, and always measure in the same spot, away from any recent addition of fertiliser that has not yet mixed in. Conductivity varies with temperature: note the temperature displayed at the same time as the reading, so that you compare measurements taken under similar conditions. Record your values in a notebook or spreadsheet, as it is their change from one week to the next that tells you most about the state of the system. Change the battery as soon as the screen dims.
🌱 In aquaponics
In aquaponics, conductivity rises as fish waste is converted into nitrates and as water evaporates; it falls when the plants take up more than they receive. If you track it every week, you can see the balance between the number of fish and the growing area. The guide to the nitrogen cycle in aquaponics explains how fish waste becomes nitrates.
Technical specifications
TDS and EC pen
- EC conductivity
- 0 to 9,999 µS/cm
- TDS
- 0 to 9,999 ppm
- Accuracy
- 2 %
- Feed
- 3 V battery included
Inline TDS
- TDS
- 0 to 999 ppm, accuracy 2%
- Fittings
- Quick-fit, 1/4 inch
- Colour indicator
- Green, blue or red
- Feed
- CR2450 coin cell battery included
Display
- Pen
- EC, TDS and temperature
- Online
- Display and colour indicator
- Inline operation
- From 0 to 50 °C
- Weight
- Pen 100 g, in-line 50 g
To budget for separately
- Rinse water
- Reverse osmosis or demineralised water
- RO unit
- Compact reverse osmosis unit
6 further specifications are available in the detailed view.
In the box
- 1 ARKA myAqua tester in the chosen model, battery included
- 2 adapters with the online tester
Ranges, accuracy and power supply noted on 10/10/2026 from the manufacturer's instructions and technical datasheets.
Which tester for your water?
Two uses: measuring from time to time, or monitoring a reverse osmosis unit.
Which tester?
One answer, and the table highlights the reference that suits you.
| Measurement | TDS range (ppm) | EC conductivity | Price | |
|---|---|---|---|---|
| Recommended TDS and EC penYour choice | One-off, in a glass or in the tank | 9999 ppm | Yes | ¥2,700 |
| Inline TDSYour choice | Continuous, on the RO unit | 999 ppm | No | ¥5,400 |
TDS and EC penRecommended
Use
MeasurementOne-off, in a glass or in the tank
TDS range (ppm)9999 ppm
EC conductivityYes
Inline TDS
Use
MeasurementContinuous, on the RO unit
TDS range (ppm)999 ppm
EC conductivityNo
2% accuracy on both devices.
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Frequently asked questions
6 questions
6 key questions
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