Editor's Choice - Our Favorite Instant 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 [star rating='3.8']
• Quality [star rating='3.3']
• Value For Money [star rating='3.4']
• Affordability [star rating='4.5']

Peoples Choice - Other Highly Rated Instant Aquarium Hydrometers

2. KKmoon Salinity Refractometer, Handheld Seawater Hydrometers, Optical Salinity Tester, Portable ATC ...

User Ratings: 70 8

KKmoon First Impressions

"Decent case."

Hate the batteries, but once loaded, it seems to work fine. Get precise salinity readings in moments. I have a 2000+ gallon pond and I just put salt in it last month. The hydrometer is good, but I ordered two Shrimp CRS Miniature glass figurine, Clear. So once your instant ocean shows a measurement. All very easy and I feel as though I am getting an accurate salinity reading. The reading is big enough for you to read and it comes with the batteries.

• KKmoon Salinity Refractometer, Handheld Seawater Hydrometers, Optical Salinity Tester, Portable ATC Refractometer, Dual Scale Saltwater Tester for Aquarium, Seawater, Pool, Fish Tank
• Measure salt water or salinity of water, ideal for aquariums and marine monitoring.
• With measurement level for direct reading. Adjustable manual focus, easy to focus and calibrate.
• Handheld design and non-slip rubber handle for easy operation.
• Instant Reading Result: Just need 2-3 drops of solution and a few seconds, you can get accurate readings.
• Built-in automatic temperature compensation(ATC) to get faster results.
• Manufacture: KKmoon
• Item Weight: 8.9 ounces

• Editor's Impressions Of The KKmoon
• Accuracy [star rating='4.4']
• Quality [star rating='4']
• Value For Money [star rating='3.8']
• Affordability [star rating='4.8']

3. Aquarium Refractometer, Seawater Salinity Meter Aquarium Optics Refractometer Temperature ATC Digita...

Hongzer First Impressions

"Easy to use."

Functions just as it is supposed to. It is essential to get some specialized aquarium calibration fluid for 1. It is easy to read and perform the procedure in seconds. It did not need adjusting to calibrate, though I tried to just to see how it worked. Once I figured that out, it works great. Be sure to buy the calibration solution and test this before use! So once your instant ocean shows a measurement.

• Aquarium Refractometer, Seawater Salinity Meter Aquarium Optics Refractometer Temperature ATC Digital 0-10%
• 0 to 10% salinity, 0.01% scale.
• Durable aluminum body, durable and can use for a long time.
• Adjust the focus by twisting the handle.
• Compact design with rubber handle.
• Soft and flexible eyepiece for added comfort. Instant and reliable aqueous solution measurement.
• Manufacture: Hongzer
• Item Weight: 8.4 ounces
• Product Dimensions: 6.69 x 1.57 x 1.57 inches

• Editor's Impressions Of The Hongzer
• Accuracy [star rating='5']
• Quality [star rating='5']
• Value For Money [star rating='5']
• Affordability [star rating='5']

Here Are Some Other Related Aquarium Hydrometers

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 [star rating='5']
• Quality [star rating='4.9']
• Value For Money [star rating='3.9']
• Affordability [star rating='4.7']

5. Aquarium Refractometer, Seawater Salinity Meter Aquarium Optics Refractometer Temperature ATC Digita...

Hongzer First Impressions

"Easy to use."

Functions just as it is supposed to. It is essential to get some specialized aquarium calibration fluid for 1. It is easy to read and perform the procedure in seconds. It did not need adjusting to calibrate, though I tried to just to see how it worked. Once I figured that out, it works great. Be sure to buy the calibration solution and test this before use! So once your instant ocean shows a measurement.

• Aquarium Refractometer, Seawater Salinity Meter Aquarium Optics Refractometer Temperature ATC Digital 0-10%
• 0 to 10% salinity, 0.01% scale.
• Durable aluminum body, durable and can use for a long time.
• Adjust the focus by twisting the handle.
• Compact design with rubber handle.
• Soft and flexible eyepiece for added comfort. Instant and reliable aqueous solution measurement.
• Manufacture: Hongzer
• Item Weight: 8.4 ounces
• Product Dimensions: 6.69 x 1.57 x 1.57 inches

• Editor's Impressions Of The Hongzer
• Accuracy [star rating='5']
• Quality [star rating='5']
• Value For Money [star rating='5']
• Affordability [star rating='5']

6. Ade Advanced Optics aaosal-B Automatic Temperature Compensation Sea Water Salinity Refractometer for...

User Ratings: 26 41

Ade Advanced Optics aaosal-B First Impressions

"Be well my friend."

Comes with a nice carrying case for easy and secure transportation. I have gone two years in this hobby with a hydrometer. It says in the instructions to use distilled water. Good quality and simple to use refractometer. The refractor was off out off the box. It is heavy and easy to read in any light. I use this for my 10g brackish and it works ok.

• Ade Advanced Optics aaosal-B Automatic Temperature Compensation Sea Water Salinity Refractometer for Aquarium, 0% - 10% and 1.0 to 1.070 S.G. Dual Scale Hydrometer, Black
• Manufacture: Ade Advanced Optics

• Editor's Impressions Of The Ade Advanced Optics aaosal-B
• Accuracy [star rating='2.2']
• Quality [star rating='3.2']
• Value For Money [star rating='3.5']
• Affordability [star rating='3.1']

7. Rhino Clinical Pet (Dog & Cat) Refractometer HR305 (ATC), Urine Specific Test

RHINO TECHNOLOGY First Impressions

"Easy to use."

If you let it sit in the tank overnight, it definitely gives an accurate reading. It's perfectly accurate based on the known calibration fluid. Functions just as it is supposed to. Plenty of info on YouTube and the web if you don't know how. I don't want to deal with temperature correction or. I've tried several different refractometers now and they are mostly the same. YOU WILL NOT get an accurate reading if there are bubbles on the needle.

• Rhino Clinical Pet (Dog & Cat) Refractometer HR305 (ATC), Urine Specific Test
• The Rhino Pet refractometer HR305 can be used to read Specific Gravity of Dog Urine, Specific Gravity of Cat Urine,and Serum or Plasma Protein.
• We provide 2 years quality warranty and customize services for the Pet refractometer.
• The surface of the refractometer is sprayed with Teflon,It has the characteristics of wear resistance, corrosion resistance, anti-static and anti-adhesion.
• The Rhino Pet hand-held Refractometer come with portable holster, water bottle, calibration mini-screwdriver, english instruction manual, cleaning cloth, plastic pipette and case.
• Rhino Pet refractometer with Automatic Temperature Compensation ( 50°F~86°F / 10°C~30°C ).
• Manufacture: RHINO TECHNOLOGY

• Editor's Impressions Of The RHINO TECHNOLOGY
• Accuracy [star rating='5']
• Quality [star rating='4.4']
• Value For Money [star rating='5']
• Affordability [star rating='5']

8. 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']

9. Seawater Salinity Refractometer,V-Resourcing Automatic Temperature Compensation Sea Water Salinity M...

User Ratings: 64 8

V·RESOURCING COMINHKPR127692 First Impressions

"Good product."

I have tried others before but this has given me accurate and stable results. All very easy and I feel as though I am getting an accurate salinity reading. I did NOT calibrate, but am getting accurate readings. YOU WILL NOT get an accurate reading if there are bubbles on the needle. I run brackish tanks and it works perfectly. 027, I'm so glad I bought this one and it came spot on. Definitely a lot cheaper than a refractometer.

• Seawater Salinity Refractometer,V-Resourcing Automatic Temperature Compensation Sea Water Salinity Measurer for Aquarium, Hydrometer, 0-100ppt & 1.000-1.070 Salinity Specific Gravity
• Automatic Temperature Compensation: 10℃~30℃
• Measuring range: salinity: 0-100 ‰, Specific Gravity : 1.000 to 1.070
• Minimum scale: salinity: 1 ‰, Specific Gravity : 0.001
• Resolution: salinity: ±1‰, Specific Gravity : 0.001 mm
• Perfect for salty water tank and aquarium, seafood water tank, salty pools & spas and etc
• 1*Salinity Refractometer
• 1*Mini-screwdriver
• 1*Pipette
• Manufacture: V-Resourcing
• Product Dimensions: 8 x 3 x 2 inches; 8 Ounces

• Editor's Impressions Of The V·RESOURCING COMINHKPR127692
• Accuracy [star rating='4.1']
• Quality [star rating='3.3']
• Value For Money [star rating='5']
• Affordability [star rating='5']

10. 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']