The best salinity meters, compared.
Top pick: 9-in-1 pen WQM-546 Best value: XRCLIF refractometer – Same about £13.99 shelf, ATC stated as 10–30 °C, and a full kit. Smaller sample than the top pick, and one UK review saw the zero wander. Updated October 2026.
A salinity meter tells you how much dissolved salt is in the water, in the unit that job already uses. On a UK shelf the name covers three instruments. An optical refractometer reads refractive index from two or three drops. A conductivity pen infers salinity and often adds pH, TDS, EC and temperature. A monitor adds a salinity channel you can watch away from the tank. You recognise a suitable meter by the unit, a scale that reaches the working point, and a zero or buffer you can repeat. Seawater is widely quoted at 35 ppt. A salt chlorinator is often nearer 3 to 4 grams per litre, and the cell manual sets that band. Automatic temperature compensation only helps when one temperature window is printed. A wide 0 to 100 ppt scale is not a seawater calibration. Put drops on the prism and do not immerse an optical body. A steady pH figure does not prove the salt channel. How to match the unit to the job is in the [salinity meter buying guide](/hub/measuring-equipment/salinity-meter/sub/salinity-meter-buying-guide).
A salinity meter tells you how much dissolved salt is in the water, in the unit that job already uses. On a UK shelf the name covers three instruments.
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Personal buying guide
Question 1 of 2
What are you measuring?
The Gain Express WQM-546 lists nine channels, including salinity, specific gravity, hardness, TDS, EC and COD/TOC, at £54.90. The amazon.co.uk line is 5.0 from only four reviews, and none of those bodies is from the United Kingdom. Reviewers outside the UK call the screen sharp and say a case and batteries arrived, which the specification table does not confirm. pH is not among the nine named channels, so this is not the pool pH pen the other rows are. A salinity range is not printed. The bullets say conductivity is used for minerals and salinity, and UV absorbance for COD, TOC and UV275. Four perfect stars are not a sample you can lean on for a reef or a salt cell. Treat it as a multi-parameter pen with almost no UK evidence, not as the top of this table.
Pros
Cons
Best for: Someone who wants several water channels in one pen and will not treat four stars as proof
Less suitable: A reef or salt cell that needs a checked salinity number
Specifications
Common questions
Does this pen measure pH?
pH is not among the nine channels named in the bullets.
How is salinity obtained, according to the listing?
The bullets say electrical conductivity is used for minerals and salinity, and UV absorbance for COD, TOC and UV275.
How many amazon.co.uk reviews are on the listing?
5.0 from 4 reviews. None of the four review bodies is from the United Kingdom, and none describes a fault.
HXTDBY’s optical meter is £17.85, states that no battery is needed, and shows 0–100 ppt with specific gravity 1.000–1.070. The star line is 4.8 from 38 reviews, with 12 United Kingdom bodies in the notes. Several of those call it easy to calibrate for marine fish, coral salt and amano shrimp larvae, and reviewers name a plastic case, pipette, screwdriver, cloth and instructions. One UK buyer could not get the scale below specific gravity 1.005 on RO water, so that unit cannot be zeroed. The lens cover is called frail, and the specification table says Plastic while the bullets say aluminium and ABS. ATC is claimed without a temperature window. A high star line on 38 reviews does not outweigh a zero you cannot reach. Buy it only if the boundary will sit on the fresh-water mark, and send it back to the seller if it will not.
Pros
Cons
Best for: An optical check you can zero on RO water before you trust a marine reading
Less suitable: Anyone choosing it only because 4.8 is the highest star line in the set
Specifications
Common questions
Does it need batteries?
The bullets say no battery is needed. You put two or three drops on the prism and use light.
What did a UK review say about zeroing?
One buyer could not get the scale below specific gravity 1.005 on RO water. Other UK reviews call it easy to calibrate. Listing rating 4.8 from 38 reviews.
Is the material one answer?
The specification table says Plastic. The bullets say aluminium and ABS rubber. Both are on the listing.
The listing titled Aqueous Lab, with the brand field Agriculture Solutions and model WL0020-ATC, is an optical refractometer at £13.99 for seawater and marine fishkeeping, with 0–100 ppt in the title. It is 4.6 from 4,704 amazon.co.uk ratings, the largest sample in this comparison, though the review notes hold only a few bodies rather than all 4,704 texts. Those bodies say the hard case, dropper, screwdriver, manual and cloth are enough to mix saltwater at home once you zero it. A UK reviewer says the fresh-water zero has to be at the same temperature as the sample. One unit in the notes arrived with a broken internal lens, and another buyer returned it after it disagreed with other meters. The brand line and the title do not match, so you are buying the model code as much as a single brand name. It is the top pick here because the review count and the kit are both on the listing, not because a laboratory ranked its accuracy.
Pros
Cons
Best for: A home marine mix when you will zero on fresh water at the same temperature as the sample
Less suitable: A buyer who wants one brand name on the title, the box and the brand field
Specifications
Common questions
Which name is on the listing?
The title says Aqueous Lab. The brand field says Agriculture Solutions. The model is WL0020-ATC. The manufacturer field says ATC.
What must you do before trusting it, according to a UK review?
Calibrate against fresh water at the same temperature as the sample. The listing rating is 4.6 from 4,704 reviews. The review notes only include a few bodies.
What is in the box?
Hard case, dropper, screwdriver, user manual and cleaning cloth.
BOWONG’s refractometer is £13.99 with 0–100‰ at 1‰ steps and specific gravity 1.000–1.070 at 0.001, marked D 20/20. The listing is 4.5 from 20 reviews, and the review notes have a single United Kingdom review that calls the reading good and does not describe a fault. That is a thin sample next to the Agriculture Solutions row at the same price. ATC is printed twice and the windows disagree: one sentence says 0–10 °C and another says use it at 10–30 °C. The page asks about a case and does not answer, so the box contents stay unknown. Plastic is the material in the specification table. It can sit as a spare optical meter if the scale is sharp when it arrives. Twenty reviews and a split temperature claim are not the same evidence as a 4,704-review listing at £13.99.
Pros
Cons
Best for: A second optical meter at the floor price if the ATC window you need is the one you can verify
Less suitable: A first marine meter when you want a large review sample and a known kit
Specifications
Common questions
What ATC window is printed?
One sentence says within 0–10 °C. Another says use it at 10–30 °C. Both stay in the data.
Is a case included?
The listing asks and does not answer. The box contents are not stated.
What is the review sample?
4.5 from 20 reviews. The review notes have one UK review, which calls the reading good and does not describe a fault.
YINMIK’s YK-T5BEU is the dearest 5-in-1 pen in this set at £36.99, listing pH, salinity, TDS, EC and temperature, with ATC given as 32–122 °F. The star line is 4.3 from 625 reviews, and 16 United Kingdom bodies were used for the themes. Some buyers say it arrived already calibrated, and reviewers mention buffer pots even though the specification table does not itemise them. The same UK set includes a pH 4.0 buffer that stored as 7.0, a unit stuck on 7.0 after about two months, and readings that drifted after only a couple of measures. A numeric salinity range is not printed. A two-year warranty is a bullet, not a checked UK term in these notes. It suits a pool or kitchen pH check when a two-point calibration holds. It is a weak choice if the salt number has to stay put after the second dip.
Pros
Cons
Best for: Pool or kitchen pH checks if you can make a two-point calibration stick
Less suitable: Anyone who needs a stable salinity figure after a few dips
Specifications
Common questions
What does the meter claim to read?
pH, salinity, TDS, EC and temperature, with ATC stated as 32–122 °F.
Did UK reviews get pH calibration to stick?
Some say it arrived calibrated. One could not make the pH 4 buffer stay at 4.0, and another unit stuck on 7.0. Listing rating 4.3 from 625 reviews.
Is the 2-year warranty a checked fact?
It is a sentence in the bullets. These notes do not confirm a UK warranty term beyond that sentence.
The UIUZMAR UI-09A prints 0–9990 ppm, 10.1–100.0 ppt and 0.0–15% salinity, plus pH, EC, TDS and temperature, at £29.99. It is 4.3 from 406 amazon.co.uk reviews, and the review notes hold eight United Kingdom review bodies. Pond keepers say the pH powder in the box makes the reading clearer than colour strips, and they use it after calibration for a salt dose they already know. One UK reef reviewer said pH was usable and salinity was not close enough for the tank. Setup takes a while, and you still have to interpret the number yourself. The bullets also repeat a pool band of 2700–3400 ppm and reef examples of 32–35 ppt. Those are listing examples, not a standard. It is a pond and pool pen with powder included, and a weak stand-in for seawater if that reef review matches your tank.
Pros
Cons
Best for: A koi pond or salt pool when you will calibrate pH before you trust the salt figure
Less suitable: Reef salinity near 35 ppt
Specifications
Common questions
What salinity range is printed?
0–9990 ppm, 10.1–100.0 ppt and 0.0–15%. The bullets also name pool salinity 2700–3400 ppm and reef examples of 32–35 ppt.
What is in the box?
The listing says the pH salt meter, a manual and pH calibration powder.
Do UK reviews trust the salinity channel for a reef?
One UK reviewer said pH was fine and salinity was not close enough for a reef. Others use it on ponds after calibration. Listing rating 4.3 from 406 reviews.
The UIUZMAR UMR-PH09 is a 5-in-1 pen for salinity, pH, TDS, EC and temperature at £27.99. The listing names a pool band of pH 7.2–7.8 and salinity 2700–3400 ppm, which is the bullet’s ideal, not a UK rule. The amazon.co.uk line is 4.3 from 294 reviews, though the review notes hold only one United Kingdom review body. That review checked it against NT Labs kits and said salinity and pH drifted within about two days, while temperature stayed closer. Other bodies in the notes call it quick to read and fine for a pool when calibration holds. Waterproofing is asked on the page and not answered, and the box contents are not itemised. A steady temperature figure does not prove the salt channel. Treat it as a pool pen you will buffer again, not as a reef reading near 35 ppt.
Pros
Cons
Best for: Salt-pool pH and ppm checks when you will recalibrate
Less suitable: A reef that needs a stable reading near 35 ppt
Specifications
Common questions
Which pool numbers does the listing name?
pH 7.2–7.8 and salinity 2700–3400 ppm. Those are the bullet’s ideals, not a UK rule.
Is waterproofing stated?
The listing asks the question and does not answer it. Do not assume a rating.
What did the UK review say about accuracy?
One UK review said salinity and pH drifted within about two days against NT Labs kits, and that temperature stayed closer. The listing rating is 4.3 from 294 reviews.
The XRCLIF refractometer is £13.99 with a stated scale of 0–100 ppt and specific gravity 1.000–1.070, and ATC printed as 10–30 °C. The listing is 4.3 from 167 reviews, with nine United Kingdom bodies in the notes. The box list is concrete: refractometer, screwdriver, pipette, manual, cloth and a hard case. UK reviewers mix saltwater for amano shrimp and marine tanks and call it straightforward at this price, though one says the manual is hard to follow. One UK review is the limit you should keep: deionised water read anywhere from 1.000 to 1.007 and needed calibration every time. That is a zero that wanders, not a reason to skip the screwdriver. It is the best value optical kit here when you want the temperature window written down and you will check the zero before a marine reading. The title does not say natural seawater or PSU.
Pros
Cons
Best for: A budget marine or shrimp check when you will zero it on deionised water inside 10–30 °C
Less suitable: Someone who will not recalibrate before a reading that animals depend on
Specifications
Common questions
What is the ATC window?
The bullets state 10 °C to 30 °C (50 °F to 86 °F).
What comes in the box?
Refractometer, calibration screwdriver, pipette, manual, cleaning cloth and a hard case.
Do UK reviews say the zero holds?
Several call it easy for shrimp and marine water. One says deionised water read anywhere from 1.000 to 1.007 and had to be calibrated every time. Listing rating 4.3 from 167 reviews.
The YINMIK YK-5SEU listing records ASIN B0CN4NJZ89 and a product URL for B0C6P4V4FR, so the code in Additional Information and the code you click are not the same. At £28.99 it is 4.1 from 1,119 reviews, the largest pen sample here, with 23 United Kingdom bodies noted and the first 16 used for themes. Koi keepers say pond pH and a quarantine salt dose are easier than strips, including one colour-blind jacuzzi user. One UK reviewer compared it with a Hanna instrument and said salinity and temperature were off, while pH could still be calibrated. Another expected ppt and could only see ppm and percent. Factory calibration was off in more than one review, including a pH 7 standard read as pH 10. Six pH powder packs are claimed. It is a heavily reviewed pond and pool pen if you accept ppm, and a page you should open carefully because the two codes do not match.
Pros
Cons
Best for: Pond or salt-pool pH and ppm after you have checked which ASIN the live page is
Less suitable: A reef keeper who needs ppt on the screen
Specifications
Common questions
Which ASIN should a link use?
The listing ASIN line is B0CN4NJZ89. The product URL is amazon.co.uk/dp/B0C6P4V4FR. Both are recorded. They are not the same code.
Can the screen show ppt?
One UK reviewer expected ppt and could only see ppm and percent. The listing still talks about salinity.
How did salinity compare with a Hanna meter in reviews?
One UK reviewer said salinity and temperature were off against a Hanna instrument, while pH could be calibrated. Listing rating 4.1 from 1,119 reviews.
The QWORK WD41636 reads two or three drops on a dual scale of 0–100 ppt and specific gravity 1.000–1.070, listed at £14.95. Across 125 amazon.co.uk reviews the line is 4.0, and the review notes hold 14 United Kingdom review bodies. Several of those buyers use it at water changes and call it easy to wipe once the boundary is sharp. The same bodies keep returning to a loose body, a tilted line, and a viewing window that will not focus, including a unit that failed after about a month. ATC is claimed, but no temperature window is printed, and the box contents are not listed. A prism you cannot focus is a return under the Consumer Rights Act 2015, not a technique you can practise your way out of. It is a cheap optical check only when the scale line sits straight.
Pros
Cons
Best for: Home saltwater mixes when you can see a straight boundary on the scale
Less suitable: Anyone who needs a printed ATC window or a kit list on the listing
Specifications
Common questions
What scales does the QWORK listing state?
0–100 ppt at 1 ppt resolution and specific gravity 1.000–1.070 at 0.001. ATC is claimed. A temperature window is not stated.
Does the listing say it needs batteries?
No battery claim is printed. The method described is two or three drops, not a powered probe.
What do the UK reviews repeat?
Ease of use at this price, and also loose bodies, poor focus, and a tilted scale line. The listing rating is 4.0 from 125 reviews.
The TEKCOPLUS TK525PLUS_R1 is an 8-in-1 Wi-Fi monitor at £115.99, listing pH, temperature, TDS, EC, salinity, ORP and specific gravity, with a Tuya app on 2.4 GHz only. The star line is 3.7 from eight reviews. One UK review likes seeing the parameters in the app and calls pairing simple. Another review in the notes, not from the UK, describes pH and ORP jumping by about 0.5 pH and 50 mV within a minute. That is one stability complaint, not a failure rate. The listing claims salinity accuracy of ±2% of full scale, which is the seller’s sentence, and pH at ±0.05. Printed weight is 0.73 g, which cannot describe a housing listed at about 25 cm long. Batteries are said to be neither included nor required, any other supply is not stated, and eight reviews do not make this a premium salinity pick for someone who mainly wants a phone graph.
Pros
Cons
Best for: A tank or hydroponic setup where you want app readings and will check them another way
Less suitable: A buyer paying £115.99 for a proven salinity reading
Specifications
Common questions
Which Wi-Fi does the listing allow?
The Tuya app, and only 2.4 GHz. 5 GHz is not claimed.
What accuracy does the listing claim for salinity?
±2% of full scale. That is the manufacturer sentence, not an independent test. pH is claimed at ±0.05.
How large is the review sample?
3.7 from 8 reviews. One UK review likes the app. One other review describes pH and ORP jumping. The printed weight is 0.73 g.
The Lazmin112 pen is listed at £28.50 with a range of 0–199.9 ppt and a Celsius/Fahrenheit switch. The title leads with drinking water, while the bullets also name pools, fish ponds and seawater. The amazon.co.uk line is 3.3 from three reviews. The only review body is a United Kingdom title that says very poor for koi keepers and then repeats that phrase without describing the fault. Dimensions are printed as 1 × 1 × 1 cm, which is not a usable size, and the brand field is empty. ATC is not stated, calibration is not stated, and batteries are described as neither included nor required. There is almost nothing you can check before you buy except the 0–199.9 ppt claim. Leave it until a larger UK sample exists if the pond or the reef is the reason you are searching.
Pros
Cons
Best for: Only a buyer who already knows this probe style and will test it against a known solution
Less suitable: Koi keepers and reef keepers choosing from this comparison
Specifications
Common questions
What range is stated?
0–199.9 ppt, with the probe placed in the liquid, and a Celsius/Fahrenheit switch.
Who makes it, on the listing?
The manufacturer line says Lazmin112. There is no separate brand line. Dimensions are printed as 1 x 1 x 1 cm.
What do the reviews say?
3.3 from 3 reviews. The only review body says very poor for koi keepers and does not describe the fault.
Twelve salinity-meter listings on amazon.co.uk were scored on 21 October 2026 from listing facts and review notes, not from a laboratory test or an accuracy ranking. Amazon stars are capped so a thin sample cannot carry the score, then review count, what the listing states, and review sentiment are weighted 40, 25, 20 and 15. Points come off when the listing ASIN and the product URL disagree. No points are added for UKCA, an IP rating or a British Standard, because none is printed on these listings. Each star line stays the amazon.co.uk figure. The 0–100 score is this listing score.
Amazon star line
40%Up to 40 points from the amazon.co.uk star average, capped so 5.0 cannot carry a thin sample. Under 10 reviews, the star line is not allowed to produce a score near 100.
Review count
25%Up to 25 points from the review count on that listing. 4,704 ratings score at the top of this band. Fewer than 10 reviews score near the bottom.
What the listing states
20%Up to 20 points for a salinity unit, a single ATC window, and a calibration tool or powder in the box. A split ATC window or a missing range scores less.
Review sentiment
15%Up to 15 points from the review notes, with deductions when a UK body reports a zero that will not move, a salinity channel that misses a reef or a Hanna check, or a pH calibration that will not hold.
Match the unit to the water before you read the stars. A reef, a salt cell and a koi dose are not the same number, and a pen that shows pH has not proved the salt channel. The notes below follow the listing facts from 21 October 2026. None of the scores is a laboratory test.
A salinity meter on amazon.co.uk is an optical refractometer, a conductivity pen that also shows pH, or a monitor with a salinity channel. Buyers are reef keepers, salt-pool owners, koi keepers who already have a dose, and people who also want EC or pH. Judge it by the unit the job uses, whether you can zero or buffer it, and whether a seawater scale is actually claimed. Seawater is widely given as 35 ppt, while a salt chlorinator is often near 3–4 g/L.
Seawater at 35 ppt is 35,000 ppm. A salt chlorinator is often near 3–4 g/L, which is a different band. A pen that shows ppm is not automatically a reef meter, and a 0–100 ppt refractometer is not automatically a pool meter.
A UK review of the largest optical sample says the fresh-water zero has to be at the same temperature as the sample. ATC only helps when one temperature window is printed. Two windows on the same listing are not one claim.
UK review notes on the pens include drift against test kits, a reef channel that was not close, and a Hanna check where salinity was off while pH could still be calibrated. Buffer pH on its own. Do not copy 2700–3400 ppm onto a cell with a different manual.
The first check is the unit the water already uses. Reefs are discussed in ppt or specific gravity at a stated temperature. Salt cells are discussed in ppm or grams per litre, and the cell manual sets the band. If the meter cannot show that unit, it is the wrong meter. A refractometer reads refractive index from two or three drops and does not give pH. A pen infers salinity from conductivity and often adds pH, TDS, EC and temperature. A monitor adds a channel you can watch away from the tank.
You should be able to repeat the check. Zero a refractometer on RO or deionised water, then check near the working point if animals depend on the number. Match that zero to the sample temperature. A screwdriver, pipette and cloth in the box list are the practical kit. A pen needs buffers or powder, and a good pH reading still does not prove salinity.
Three typical situations, each with a recommendation from this comparison.
You want ppt on an optical scale and a kit the listing actually names. The Agriculture Solutions WL0020-ATC, titled Aqueous Lab, is about £13.99, with 4.6 from 4,704 reviews, a hard case, dropper, screwdriver, manual and cloth. Zero it on fresh water at the same temperature as the sample. The score is review volume plus that kit, not a lab accuracy rank.
You want the temperature window written down at the same shelf price. The XRCLIF refractometer is about £13.99, with ATC stated as 10–30 °C, a case, pipette, screwdriver and cloth, and 4.3 from 167 reviews. One UK review saw deionised water wander from 1.000 to 1.007, so check the zero before a reading animals depend on.
You need ppm and pH, and you will calibrate before you trust the salt figure. The UIUZMAR UI-09A is about £29.99, with a stated span of 0–9990 ppm and 10.1–100.0 ppt, pH powder in the box, and 4.3 from 406 reviews. A UK reef review said the salinity channel was not close enough near 35 ppt.
In this set of twelve amazon.co.uk listings, the top pick is the Agriculture Solutions WL0020-ATC optical refractometer, titled Aqueous Lab, at about £13.99. The listing is 4.6 from 4,704 reviews and names a hard case, dropper, screwdriver, manual and cloth. That is review volume plus a stated kit, not a measured accuracy win, and the title and the brand field do not match. The best value is the XRCLIF refractometer, also about £13.99, with ATC stated as 10–30 °C and a full kit, on a smaller sample of 4.3 from 167 reviews and one UK report of a wandering zero. Pens in this set are for ppm and pH when you will recalibrate. None of these scores is a lab test, and a 0–100 ppt title is not a seawater calibration.
XRCLIF refractometer
Same about £13.99 shelf, ATC stated as 10–30 °C, and a full kit. Smaller sample than the top pick, and one UK review saw the zero wander.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources from the research digest, last checked on 21 October 2026. Shelf prices and star lines are the amazon.co.uk figures captured with these twelve listings. The price bands are this set, not a market average.
This page contains affiliate links to amazon.co.uk. If you buy through them, we may earn a commission at no extra cost to you. Prices, stars and review counts are from the UK listings checked on 21 October 2026. We did not lab-test these salinity meters.
