Editor's Choice - Our Favorite Instant Ocean Aquarium Hydrometers

1. Instant Ocean SeaTest Hydrometer

User Ratings: 59 6

Instant Ocean TK-504 First Impressions

"Calibrate it, use it."

Make your own by simply boiling some water and collecting the condensate. This one here was much cheaper,& exactly the same as they sold in the store. My only criticism would be that it's a little too dark. Normally that gives the more accurate reading. Used distilled water to calibrate, the screw is located under the rubber cap. Once I adjusted the refractometer, my aquarium salinity read 1. Hate the batteries, but once loaded, it seems to work fine.

  • Instant Ocean SeaTest Hydrometer
  • Marine hydrometer: Tests salinity and specific gravity in marine aquariums to help maintain a healthy tank
  • Accurate: Precise, full-range readings - accurate to +/- 0
  • Ready to use: Simply dunk in aquarium to fill with water, then set on level surface to read
  • Easy to read: Clearly marked to show results
  • Extra-wide stabilizer base: Two-color scale with a safe zone for simple results
  • Manufacture: Instant Ocean
  • Item Weight: 0.8 ounces
  • Product Dimensions: 6.3 x 4.2 x 1.3 inches
  • Editor's Impressions Of The Instant Ocean TK-504
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

Instant Ocean TK-504 Final Thoughts

"Good price."

Simple to use, but if there are any air bubbles the results will be way off. The instant ocean hydrometer will always be right. 026 with the new Aquatic Experts fluid. Now its easy to make sure I have the correct amount of salt in my aquariums. Looks to provide very accurate readings. Easy to use, easy to clean, easy to read. My only criticism would be that it's a little too dark.

Overall Score
4.2


(426 Points)

2. capetsma Salinity Tester, Accurate Sea Hydrometer Aquarium Marine Salinity Meter for Fish Tank Pond ...

User Ratings: 56 11

capetsma First Impressions

"Great Product, Thanks!"

Be sure to adjust the focus by turning the eye focal when you first receive. There are conversion charts and tables online. I have gone two years in this hobby with a hydrometer. Get precise salinity readings in moments. It is a little cheaper made but it works great for the cost! Make your own by simply boiling some water and collecting the condensate. There are conversion charts and tables online.

  • capetsma Salinity Tester, Accurate Sea Hydrometer Aquarium Marine Salinity Meter for Fish Tank Pond Water Saltwater Freshwater Specific Gravity Test
  • Safe Material & Unique Design: Made of durable Acrylic, this Fish Tank Test Kit salinity Hydrometer is designed with an automatic level function.
  • Quickly, easily, and accurately measurement: With this hydrometer saltwater aquarium test kit, you can test your marine aquarium's salt level and specific gravity, and It is optimum to be put into below 6" deep water to avoid the error caused by the oil film on the water.
  • Higher Accuracy & safe zone indicated: Readings are temperature-corrected & accurate to +/- 0. 001. specific gravity units ranges from 1. 000 - 1. 030 with a safe zone of 1.020-1.023. The outside range of scale indicates salinity ppt, ranges from 0-40, safe zone is 27-31.
  • Easy to Read & Clean: The easy-to-read swing-arm pointer and extra wide stable base provide an accurate test result. After use, soak this saltwater meter in mild acid(vinegar) for 30 minutes, rinse with tap water and air dry. Do not disassemble.
  • Wide Usage:Fit for brackish and reef salt marine aquariums. Perfect for testing both salinity and specific gravity of your brackish and marine tank.Includes salinity and specific gravity scales.Suitable for fresh water and sea water.
  • Manufacture: Capetsma
  • Editor's Impressions Of The capetsma
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

capetsma Final Thoughts

"Easy to use."

Be sure to buy the calibration solution and test this before use! If you let it sit in the tank overnight, it definitely gives an accurate reading. Plenty of info on YouTube and the web if you don't know how. Works great,& comes in a storage box. Hate the batteries, but once loaded, it seems to work fine. Too that makes it appear too cheap. So worth it considering its great quality and great price.

Overall Score
4.0


(69 Points)

3. 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
  • Quality
  • Value For Money
  • Affordability

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


(99 Points)

4. Aquarium Salinity Refractometer for Brackish/Marine/Reef Tank Testing,Hobein Dual Scale Automatic Te...

User Ratings: 68 6

Hobein First Impressions

"Calibrate it, use it."

And always make sure there is no bubbles on the measuring unit. When I compared it to what my local pet store was reading my water at it was dead on. Be sure to adjust the focus by turning the eye focal when you first receive. Plus it is super easy to use and clean. Be sure to adjust the focus by turning the eye focal when you first receive. Was calibrated and worked perfect right out of the box. It is easy to read and perform the procedure in seconds.

  • Aquarium Salinity Refractometer for Brackish/Marine/Reef Tank Testing,Hobein Dual Scale Automatic Temperature Compensation 0-100ppt & 1.000-1.070 Specific Gravity with ATC
  • ❤DUAL SCALE: Measuring Ranges: 0-100 ppt of Salinity and 1.000 to 1.070 Specific Gravity (0-10%)the reading resolution is 0.1 %. Salinity Accuracy: +/-0.1%
  • ❤APPLICATIONS: Aquariums, Marine Monitoring, Agricultural, Gardening & Educational Purposes (Biology Projects)
  • ❤EASY TO USE:Automatic Temperature Compensation (ATC),Just need 2-3 drops of solution,you will be able to read accurately the result
  • ❤PORTABLE AND DURABLE: Made with non-staining, non-corrosive and non-reactive aluminum material, light-weighted and portable, safe and durable
  • ❤PACKAGE INCLUDES: 1 Refractometer, 1 Carrying Case, 1 Calibrating Screw Driver, 2 Pippets, 1 Cleaning Clothe, 1 Instruction Manual
  • Manufacture: Hobein
  • Editor's Impressions Of The Hobein
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

Hobein Final Thoughts

"This tool does that."

Even the smallest bubble will throw the measurements way, way off. It came with all that was listed in the in production description. All very easy and I feel as though I am getting an accurate salinity reading. So once your instant ocean shows a measurement. But there are some ways to keep on getting accurate readings. Too that makes it appear too cheap. Excellent piece of equipment for the price.

Overall Score
4.4


(290 Points)

5. Salinity Refractometer for Seawater and Marine Fishkeeping Aquarium 0-100 PPT with Automatic Tempera...

User Ratings: 80 3

Agriculture Solutions WL0020-ATC First Impressions

"Would buy another!"

Very quick to calibrate and to use. I strongly recommend a refractometer vs. This is perfect to keep a check on the salt level in your tank. This device is a godsend and so much easier and cleaner to use. There are conversion charts and tables online. This requires repeatedly tapping the arm with a pencil. Great, I be had this b4 ez to test salt level.

  • Salinity Refractometer for Seawater and Marine Fishkeeping Aquarium 0-100 PPT with Automatic Temperature Compensation
  • Measure salt water or salinity of water, ideal for aquariums and marine monitoring.
  • Measures on 2 scales, Specific Gravity (D 20/20) and parts per thousand.
  • Features automatic temperature compensation.
  • Comes with hard case, dropper, screwdriver, user manual and cleaning cloth.
  • The main part is made of chromium, it's very durable.
  • Manufacture: Xin Da Cheng
  • Product Dimensions: 2 x 3 x 8 inches; 8.8 Ounces
  • Editor's Impressions Of The Agriculture Solutions WL0020-ATC
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

Agriculture Solutions WL0020-ATC Final Thoughts

"Case is handy."

Very easy, turn screw very slowly to calibrate. Used distilled water to calibrate, the screw is located under the rubber cap. It's a basic but reliable refractomer I use it for my aquariums. I don't want to deal with temperature correction or. Don't care much for having to post a review in order to activate warranty. Im using it for trying to create water conditions for amano zoes. Make sure to knock out the bubbles on the white dial by hitting it with your knuckle.

Overall Score
4.7


(1512 Points)

6. Rhinoco Salinity Refractometer, Saltwater Aquarium Refractometer, Dual Scales Specific Gravity Salin...

User Ratings: 75

Rhinoco RINTL277US First Impressions

"Great product!"

I bought this salinity meter for my aquarium. I will get one later but for now this will do, since im just starting. Get precise salinity readings in moments. Great, I be had this b4 ez to test salt level. Even the smallest bubble will throw the measurements way, way off. However, the numbers are soooo small it is sometimes hard to read. I compared the readings using this hygrometer and the calibrated refractometer.

  • Rhinoco Salinity Refractometer, Saltwater Aquarium Refractometer, Dual Scales Specific Gravity Salinity Meter with 0-100 PPT and 1.000-1.070 for Seawater, Pool, Tank, Testing, Marine Fishkeeping
  • 【Salinity Refractometer】Measure Salt Water or Salinity of Water, ideal for Aquariums, Marine Monitoring, Agricultural, Gardening & Educational Purposes.
  • 【Automatic Temperature Compensation】Salinity Tester Built-in ATC, which Accounts for Changes in Ambient Temperature and Automatically Compensates Accordingly to Guarantee Consistently Accurate Readings.
  • 【Dual Salinity Scale】Salinity Mester with Dual Scale 0-100 ppt(0 - 10 %) of Salinity and 1.000 to 1.070 Specific Gravity (0-10%).
  • 【Full Copper Chrome Plated Design】Sturdy & Compact, the Eyepiece is in High Quality for Better Viewing, Adopting Optical Glass Lens Rather than Plastic Lens for Accurate Measurement.
  • 【Accessories & Warranty】1 x Salinity Refractometer, 1 x Plastic Pipette, 1 x Mini Screw Driver, 1 x Cleaning Cloth and User Manual, Comes with 18-Month Warranty!
  • Manufacture: Rhinoco
  • Editor's Impressions Of The Rhinoco RINTL277US
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

Rhinoco RINTL277US Final Thoughts

"So far so good."

It is a little cheaper made but it works great for the cost! Simple to use, but if there are any air bubbles the results will be way off. But with alittle persistance I am able to read it. I would suggest purchasing the salt calibration solution. I got this to have a more accurate read than the hydrometer. And it is much more accurate than my old salinity meter. Waterproof if you accidentally drop it in the pool.

Overall Score
4.8


(10 Points)

7. Pen Type Salinity & Temp Meter Measurement Units Checker Quality Tester ATC for Pond Pool Saltwater ...

User Ratings: 36 25

TEKCOPLUS SMTK-49_SOL First Impressions

"So here's the verdict."

Just give me one simple, accurate reading to go by, and I'm happy. This is perfect to keep a check on the salt level in your tank. He is too cute not to want to take care of properly. Bought this as a back up refractometer. Get precise salinity readings in moments. The unit is really easy to calibrate and used. My only criticism would be that it's a little too dark.

  • Pen Type Salinity & Temp Meter Measurement Units Checker Quality Tester ATC for Pond Pool Saltwater Aquarium Cooking Seawater Drinking Water (Salinity Meter 70.0ppt + Buffer Sol'n)
  • Ideal for checking salt in fish tanks and aquariums, water monitoring, seawater-prepared food solutions, holding tanks and more!
  • Measuring Range: Salinity: 0.00~10.0 ppt (NaCL) and 10.1~70.0ppt (NaCL)
  • Auto Power-Off Function with disable feature
  • °C/°F unit switchable ,Easy one-touch calibration, Waterproof Rating: IP65
  • Calibration set: Buffer NaCI 50ppt and calibration guideline
  • Manufacture: TekcoPlus Ltd
  • Editor's Impressions Of The TEKCOPLUS SMTK-49_SOL
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

TEKCOPLUS SMTK-49_SOL Final Thoughts

"Measurement does work."

I have to recalibrate it ever use though which worries me sometimes. Just rinse with warm water afterwards. I bought this salinity meter for my aquarium. I bought this and a hydrometer because of the reviews saying its not accurate. I have gone two years in this hobby with a hydrometer. Easy to use, easy to clean, easy to read. Compare it with the refractometer and adjust the refractometer so that it matches.

Overall Score
3.6


(5 Points)

8. 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
  • Quality
  • Value For Money
  • Affordability

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


(1002 Points)

9. Digital Salinity Meter, SA287 Portable Digital Salinity Meter High Precision Salinity Temperature Pe...

Jadpes First Impressions

"Works great for reefing!"

At first, I was getting bubbles sticking to the rotating arrow. Perfrct for someone learning or anyone for that matter. Works great,& comes in a storage box. Then I made a mark on it to set the salinity of my fish tank. Bubbles can greatly affect the reading. I tried it over and over and no bubbles! I think those reviews just didn't know how to use it properly.

  • Digital Salinity Meter, SA287 Portable Digital Salinity Meter High Precision Salinity Temperature Pen Type Tester for Saltwater, Swimming Pool, Aquaculture, Aquarium
  • WATERPROOF SALINITY METER:It displays the salinity value precisely, compact size and light weight, easy and portable to carry, convenient to use.This instrument can not only detect the salt content of edible salt, salt water pool and koi fish pond, but also the salinity of seawater, marine, salt water fish tank salt level testing.
  • SALINITY TESTER:Digital Salinity Tester for Salt Water.The pen type salinity meter is a precision instrument for testing the salinity value of a solution.Quick and reliable manner for most regular water solutions' testing.
  • WIDE APPLICATIONS:Suitable for saltwater, swimming pool, aquaculture, aquarium (seawater) and pond, food processing and health care products industry. Saltwater Tester for Seawater, Aquariums, Marine Monitoring.
  • BACKLIT DESIGN:It adopts large screen LCD, PPT standard unit display, power display, power data protection function, automatic temperature compensation, dustproof and waterproof functions.
  • APPLICATION:Its full-featured performance, easy operation and replaceable electrodes make it the best choice for rapid, accurate salinity testing in laboratories, sites and schools.
  • Manufacture: Jadpes
  • Product Dimensions: 0.39 x 0.39 x 0.39 inches; 5.29 Ounces
  • Editor's Impressions Of The Jadpes
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

Jadpes Final Thoughts

"Couldn't do without it."

YOU WILL NOT get an accurate reading if there are bubbles on the needle. It did not need adjusting to calibrate, though I tried to just to see how it worked. This is perfect to keep a check on the salt level in your tank. Make sure to knock out the bubbles on the white dial by hitting it with your knuckle. My only criticism would be that it's a little too dark. It is essential to get some specialized aquarium calibration fluid for 1. I have purchased before will buy again!

Overall Score
3.0


(1 Points)

10. 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
  • Quality
  • Value For Money
  • Affordability

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


(265 Points)

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