Editor's Choice - Our Favorite ONE250 Aquarium Hydrometers

1. Premium Salinity Refractometer with Automatic Temperature Compensation for Saltwater, Aquarium, Mari...

User Ratings: 75 9

ONE250 First Impressions

"Arrived quickly."

I HIGHLY recommend this to Aquarists! Find a good light source to make reading easier. But with alittle persistance I am able to read it. My corals will be much happier now. I would recommend this product to anyone that has a marine aquarium. It's perfectly accurate based on the known calibration fluid. When I compared it to what my local pet store was reading my water at it was dead on.

  • Premium Salinity Refractometer with Automatic Temperature Compensation for Saltwater, Aquarium, Marine Reef Tank Testing - Dual Scale (0-100ppt & 1.000 to 1.070 S.G.)
  • ✔ Hand-held analog salt meter; Light-weight, portable, includes protective carrying case
  • ✔ Measures concentration of salt and dissolved solids in aqueous solution
  • ✔ Provides reading in parts per thousand (0-100PPT) and specific gravity (1.000 to 1.070 SG)
  • ✔ Ideal for on-site measurements in processing and storage areas, or in the field
  • ✔ Determine salinity during preparation of pickles, seafood products, frozen vegetables and fruits
  • Manufacture: ONE250
  • Product Dimensions: 8 x 3 x 2 inches; 9.14 Ounces
  • Editor's Impressions Of The ONE250
  • Accuracy [star rating='4']
  • Quality [star rating='5']
  • Value For Money [star rating='5']
  • Affordability [star rating='4.2']

ONE250 Final Thoughts

"This tool does that."

Compare it with the refractometer and adjust the refractometer so that it matches. On the shaft of the refractometer, there's a little, rubber-covered nub. I bought this refractometer as a more accurate option for salinity than a hydrometer. Be sure to buy the calibration solution and test this before use! Bought this as a back up refractometer. 026 with the new Aquatic Experts fluid. I felt it wasn't accurate which was verified by my LFS.

Overall Score
4.5

[star rating="4.5"]
(18 Points)

2. Pen Type Salinity & Temperature Meter ATC NaCl Salt Water Quality Tester for Saltwater Aquarium Hydr...

User Ratings: 49 17

Gain Express 837-2 First Impressions

"Easy to calibrate."

Just rinse with warm water afterwards. I run brackish tanks and it works perfectly. Hate the batteries, but once loaded, it seems to work fine. I tried it over and over and no bubbles! Excellent piece of equipment for the price. The water was at what I expected it should be. 026 and the tank isn't, new animals will go into shock.

  • Pen Type Salinity & Temperature Meter ATC NaCl Salt Water Quality Tester for Saltwater Aquarium Hydroponics Food
  • MEASURING RANGE: 0~9999 ppm or 10.0ppt~100.0ppt or 0.0%~10.0% or 0.950~1.080 (S.G.) based on NaCl with ±%F.S ±1 digit / ±0.5°C Accuracy
  • DISPLAY: Dual Temperature and Salinity in four measurement units (ppm, ppt, %, S.G) / 30 x 18mm LCD Size
  • APPLICATION: Salinity measurement in fish pond, tank, aquariums, laboratories, food processing, hydroponics, Aquaculture, and other water monitoring facilities.
  • FEATURES: Waterproof IP65 / One touch calibration / Auto power off and Non-Sleep mode disable / Multi points calibration
  • POWER SUPPLY / SENSOR : 4 x LR44 button batteries
  • User friendly easy to operate with One-touch calibration
  • Manufacture: Gain Express Holdings Ltd
  • Batteries: 4 LR44 batteries required.
  • Editor's Impressions Of The Gain Express 837-2
  • Accuracy [star rating='3.2']
  • Quality [star rating='4.1']
  • Value For Money [star rating='3.2']
  • Affordability [star rating='3.8']

Gain Express 837-2 Final Thoughts

"So, it does seem to work."

But with alittle persistance I am able to read it. Perfrct for someone learning or anyone for that matter. Once I adjusted the refractometer, my aquarium salinity read 1. Works great,& comes in a storage box. Works well on my Saltwater Aquarium. It did not need adjusting to calibrate, though I tried to just to see how it worked. Would be nice if stem were slightly larger for easier read.

Overall Score
3.8

[star rating="3.8"]
(99 Points)

3. TOPINCN Square Saltwater Hydrometer Salt Water Salinity Meter Accurate Automatic Hydrometer Salt Wat...

TOPINCN First Impressions

"Super easy to use."

Then I made a mark on it to set the salinity of my fish tank. This device is a godsend and so much easier and cleaner to use. 027, I'm so glad I bought this one and it came spot on. I would recommend you to purchase this and skip the other ones. This refractor should last a good number of years. Find a good light source to make reading easier. Just rinse with warm water afterwards.

  • TOPINCN Square Saltwater Hydrometer Salt Water Salinity Meter Accurate Automatic Hydrometer Salt Water Salinity Meter for Fish Tank
  • Accurate, durable, and easy to read sea water hydrometer
  • This product is designed with an automatic level function, can automatically identify the level to avoid errors
  • Very accurate measurement readings, please rest assured to purchase
  • And each hydrometer has a laser engraved patent number
  • Fit for brackish and marine aquariums. Perfect for testing both salinity and specific gravity of your brackish and marine tanks.
  • Manufacture: TOPINCN
  • Product Dimensions: 5.51 x 3.54 x 0.79 inches; 3.17 Ounces
  • Editor's Impressions Of The TOPINCN
  • Accuracy [star rating='4.2']
  • Quality [star rating='5']
  • Value For Money [star rating='5']
  • Affordability [star rating='4.4']

TOPINCN Final Thoughts

"Case is nice as well."

The refractor was off out off the box. It works OK but seems pretty flimsy and it's feel that way. I got this to have a more accurate read than the hydrometer. This device is a godsend and so much easier and cleaner to use. Bubbles can greatly affect the reading. Be sure to adjust the focus by turning the eye focal when you first receive. Ambient room light at night is not enough and makes what you're viewing dark.

Overall Score
5.0

[star rating="5"]
(1 Points)

4. LemonBest 0%-10% Automatic Temperature Compensation Salinity Refractometer Salt Water Aquariu...

User Ratings: 75 5

LemonBest First Impressions

"Great tool."

I don't want to deal with temperature correction or. When I compared it to what my local pet store was reading my water at it was dead on. Used distilled water to calibrate, the screw is located under the rubber cap. This one here was much cheaper,& exactly the same as they sold in the store. At first, I was getting bubbles sticking to the rotating arrow. Definitely a lot cheaper than a refractometer. I decided to upgrade and it was easy to calibrate.

  • LemonBest 0%-10% Automatic Temperature Compensation Salinity Refractometer Salt Water Aquarium by Lemonbest
  • Features with automatic temperature compensation (ATC) function
  • Designed for testing the concentration of salt water and brine, ideal for aquariums, marine monitoring and quality control in research and clinical laboratories
  • With just a couple of drops of aquarium water you know exactly what the salinity is
  • Measures on 2 scales, specific Gravity (D 20/20) and parts per thousand (‰), provides a direct reading of the specific gravity and concentration of salt in water
  • Comes with a hard case, dropper, screwdriver and cleaning cloth
  • Manufacture: Lemonbest
  • Product Dimensions: 7.87 x 1.57 x 1.57 inches; 3.88 Ounces
  • Editor's Impressions Of The LemonBest
  • Accuracy [star rating='5']
  • Quality [star rating='5']
  • Value For Money [star rating='5']
  • Affordability [star rating='5']

LemonBest Final Thoughts

"Easy to use."

Make sure to knock out the bubbles on the white dial by hitting it with your knuckle. It works OK but seems pretty flimsy and it's feel that way. My only criticism would be that it's a little too dark. I don't know if that's a positive or negative but just different. Just rinse with warm water afterwards. I bought this and a hydrometer because of the reviews saying its not accurate. Pretty darn accurate for the price.

Overall Score
4.5

[star rating="4.5"]
(315 Points)

5. Fluval Sea Hydrometer for Aquarium, Medium

User Ratings: 46 17

Fluval 14356 First Impressions

"Works perfectly."

Hate the batteries, but once loaded, it seems to work fine. Like that it comes with everything needed. There are conversion charts and tables online. Now its easy to make sure I have the correct amount of salt in my aquariums. The product itself is very good quality and the included instructions are very clear. The reading is big enough for you to read and it comes with the batteries. Small problem with bubbles on the needle but other than that no issues.

  • Fluval Sea Hydrometer for Aquarium, Medium
  • Helps measure specific gravity and salt level in marine aquariums
  • Features large, easy to read markings
  • Simple design-blends in easily
  • Item Package Weight: 0.185
  • Manufacture: Fluval
  • Item Weight: 0.81 ounces
  • Product Dimensions: 1 x 5.5 x 7.9 inches
  • Editor's Impressions Of The Fluval 14356
  • Accuracy [star rating='3.5']
  • Quality [star rating='3']
  • Value For Money [star rating='2.7']
  • Affordability [star rating='3.1']

Fluval 14356 Final Thoughts

"Works great for reefing!"

Great tool if you have a salt-water fish tank or a decorative pond. I strongly recommend a refractometer vs. It works, we'll i assume it does as i have nothing to compare it to. Definitely a lot cheaper than a refractometer. Great product I used for beer making and my saltwater aquarium. It came with all that was listed in the in production description. Plenty of info on YouTube and the web if you don't know how.

Overall Score
3.7

[star rating="3.7"]
(373 Points)

6. GXSTWU Reptile Hygrometer Thermometer LCD Display Digital Reptile Tank Hygrometer Thermometer with H...

User Ratings: 71 5

GXSTWU HY-2 First Impressions

"Couldn't be happier."

I compared the readings using this hygrometer and the calibrated refractometer. But with alittle persistance I am able to read it. Not sure how accurate it is, but it's a good reference point. There are conversion charts and tables online. I will get one later but for now this will do, since im just starting. So once your instant ocean shows a measurement. Find a good light source to make reading easier.

  • GXSTWU Reptile Hygrometer Thermometer LCD Display Digital Reptile Tank Hygrometer Thermometer with Hook Temperature Humidity Meter Gauge for Reptile Tanks, Terrariums, Vivarium
  • 100% Brand New and High-Quality Reptile Tank Thermometer Hygrometer: Precise supervision of the temperature and air humidity in terrariums, vivariums and reptile tanks.
  • Stylish Design: Stylish looking digital vivarum thermometer with hook and loop for easy to install to any reptile tanks or terrariums. Comes with a battery so you can use the thermometer immediately.
  • Fantastic Value: This accurate reptile thermometer and hygrometer allows you to monitor the temperature and humidity in the reptile tanks at all times to makesure your beloved reptiles are in perfect health.
  • Fahrenheit Celsius Convertible: Temperature can be display in Fahrenheit or Celsius by press the C/F hole on the back of the item with a paper clip.
  • Quality Guaranteed: Our carefully sourced range of thermometer hygrometers are manufactured to the highest of standards our customers expect. And provide 365 days warranty, in case of any quality problems, please feel free to contact us by email, we will give you a satisfactory solution.
  • Manufacture: Cangda Electronics Co., Ltd.
  • Product Dimensions: 2.09 x 0.67 x 1.3 inches; 0.92 Ounces
  • Batteries: 1 LR44 batteries required. (included)
  • Editor's Impressions Of The GXSTWU HY-2
  • Accuracy [star rating='4.7']
  • Quality [star rating='4.7']
  • Value For Money [star rating='3.5']
  • Affordability [star rating='4.8']

GXSTWU HY-2 Final Thoughts

"Seems pretty solid."

Hate the batteries, but once loaded, it seems to work fine. If you let it sit in the tank overnight, it definitely gives an accurate reading. Like that it comes with everything needed. Get precise salinity readings in moments. I have to recalibrate it ever use though which worries me sometimes. This one read perfect, and the others were completely inaccurate. Plus it is super easy to use and clean.

Overall Score
4.4

[star rating="4.4"]
(265 Points)

7. HunterBee Salinity Refractometer for Seawater and Marine Fishkeeping Aquarium 0-100 PPT with Automat...

User Ratings: 53

HunterBee First Impressions

"Would buy another!"

And it is much more accurate than my old salinity meter. It works, we'll i assume it does as i have nothing to compare it to. I have a 2000+ gallon pond and I just put salt in it last month. Find a good light source to make reading easier. On the shaft of the refractometer, there's a little, rubber-covered nub. It works, we'll i assume it does as i have nothing to compare it to. I would recommend this product to anyone that has a marine aquarium.

  • HunterBee Salinity Refractometer for Seawater and Marine Fishkeeping Aquarium 0-100 PPT with Automatic Temperature Compensation
  • 1.for Seawater and Marine Fishkeeping Aquarium 0-100 PPT with Automatic Temperature Compensation
  • 2.Designed for direct reading of salt density in sea water.
  • 3.Rugged, durable construction - made from corrosion resistant brass.
  • 4.High contrast demarcation line for easy, accurate readings.
  • 5.Easily adjusted zero line by means of readily accessible screw.
  • Manufacture: 步仁科技
  • Editor's Impressions Of The HunterBee
  • Accuracy [star rating='3.2']
  • Quality [star rating='4.5']
  • Value For Money [star rating='3.5']
  • Affordability [star rating='3.6']

HunterBee Final Thoughts

"Good product."

Simple to use, but if there are any air bubbles the results will be way off. I bought this and a hydrometer because of the reviews saying its not accurate. Be sure to buy the calibration solution and test this before use! I felt it wasn't accurate which was verified by my LFS. I've tried several different refractometers now and they are mostly the same. On the shaft of the refractometer, there's a little, rubber-covered nub. I tried it over and over and no bubbles!

Overall Score
4.2

[star rating="4.2"]
(7 Points)

8. Hikari AccuProbe Aquarium Hydrometer, Mini

User Ratings: 55 45

Hikari 96005 First Impressions

"NO BUBBLES!"

However, the numbers are soooo small it is sometimes hard to read. Make sure to knock out the bubbles on the white dial by hitting it with your knuckle. It's fast, it's tidy, and it's accurate. I did NOT calibrate, but am getting accurate readings. Definitely a lot cheaper than a refractometer. Ultimately, the measurement was exactly the same as our old tester. Calibrate with distilled water and test every so often.

  • Hikari AccuProbe Aquarium Hydrometer, Mini
  • Ideally suited for use in Nano tanks, smaller setups or sumps of larger systems
  • Accurate to 0.001 specific gravity and salinity (PPT) measurements
  • Durable construction for extended life
  • Designed to give a temperature-corrected reading in warm water aquariums – 68°F to 85°F (20°C to 30°C)
  • Readings can be taken by taking the meter out of the aquarium and placing on a level surface or leveling the unit in the substrate
  • Manufacture: Phillips Feed & Pet Supply Natural Balance
  • Product Dimensions: 5.2 x 1 x 3.5 inches; 0.8 Ounces
  • Editor's Impressions Of The Hikari 96005
  • Accuracy [star rating='3.9']
  • Quality [star rating='3.8']
  • Value For Money [star rating='2.2']
  • Affordability [star rating='4']

Hikari 96005 Final Thoughts

"Just got it."

Next I calibrated the refractor with the calibration solution that I ordered too. Just give me one simple, accurate reading to go by, and I'm happy. Once I figured that out, it works great. So worth it considering its great quality and great price. Ultimately, the measurement was exactly the same as our old tester. Wipe down glass surface to dry it and put it back on the shelf til next time. It's a basic but reliable refractomer I use it for my aquariums.

Overall Score
3.2

[star rating="3.2"]
(2 Points)

9. Pet Dog Cat Refractometer Pet Urine Specific Gravity Refractometer Serum Plasma Protein: 2~14g/dl, C...

User Ratings: 66 16

RZ First Impressions

"Clear directions."

Trying to turn it by hand won't work. The water was at what I expected it should be. I would recommend this product to anyone that has a marine aquarium. The instant ocean hydrometer will always be right. And it is much more accurate than my old salinity meter. This requires repeatedly tapping the arm with a pencil. Bubbles can greatly affect the reading.

  • Pet Dog Cat Refractometer Pet Urine Specific Gravity Refractometer Serum Plasma Protein: 2~14g/dl, Clinical Animal Refractometer Hydrometers Urine Tester 1.000-1.060SG for Veterinary Cat Dog Pets
  • TRIPLE SCALES REFRACTOMETER: Left scale for testing urine specific gravity of large animals such as dog, the middle scale can measure cats urine specific gravity or other small animals, the right scale tests serum or plasma protein level for all animals.
  • QUICK & EASY OPERATION: few sample than other lab hydrometers, just 2 or 3 drops of solution and wait for a few seconds, accurate data automatic shows, automatic temperature compensation 0°C-30°C/50°F to 86°F
  • MEASURING RANGE: Serum or plasma protein: 2-14g/dl, large animal like dog and small animals like cats’ urine specific gravity 1.000~1.060 SG, resolution: 0.001SG. Ideal for your home pets, clinical veterinary and pet owners.
  • DURABLE REFRACOMTER: comfortable holding and non-slip ABS rubberized grip, anti-rust aluminum body for long term using. Strictly quality and safety standards approved.
  • COMPACT SIZE: Lightweight and pocket size lab refractometer, comes with sturdy plastic box, mini screwdriver, pipette and wiping cloth and manual packed together, easy to carry and storage.
  • Manufacture: RZ
  • Editor's Impressions Of The RZ
  • Accuracy [star rating='4.5']
  • Quality [star rating='5']
  • Value For Money [star rating='4.7']
  • Affordability [star rating='3.9']

RZ Final Thoughts

"These seem spot on."

I have tried others before but this has given me accurate and stable results. Now that it's calibrated I love it! I use this to check the specific gravity of my marine aquarium. Looks to provide very accurate readings. Get precise salinity readings in moments. Make your own by simply boiling some water and collecting the condensate. I use this for my 10g brackish and it works ok.

Overall Score
4.0

[star rating="4"]
(8 Points)

10. Exo Terra Terrarium Hydrometer

User Ratings: 66 5

Exo Terra PT2466 First Impressions

"Great product."

Great product I used for beer making and my saltwater aquarium. I couldn't decide between this and one of the float arm meters or both. For the price you definitley cant beat this meter is great! However, the numbers are soooo small it is sometimes hard to read. 027, I'm so glad I bought this one and it came spot on. Does just as good of a job of any meter you would buy at the store! He is too cute not to want to take care of properly.

  • Exo Terra Terrarium Hydrometer
  • Wipe clean
  • Analog hygrometer
  • Adhere the hygrometer in the terrarium
  • Clear analog dial display
  • Easy to read and install
  • Great for monitoring the humidity levels
  • Manufacture: Exo Terra
  • Product Dimensions: 0.5 x 4.1 x 7 inches; 0.64 Ounces
  • Editor's Impressions Of The Exo Terra PT2466
  • Accuracy [star rating='3.4']
  • Quality [star rating='3.9']
  • Value For Money [star rating='4.9']
  • Affordability [star rating='4.9']

Exo Terra PT2466 Final Thoughts

"Great tool."

I have a 2000+ gallon pond and I just put salt in it last month. Plus it is super easy to use and clean. Bubbles can greatly affect the reading. The water was at what I expected it should be. Does just as good of a job of any meter you would buy at the store! Simple to use, but if there are any air bubbles the results will be way off. Now its easy to make sure I have the correct amount of salt in my aquariums.

Overall Score
4.3

[star rating="4.3"]
(1002 Points)

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