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 [star rating='3.8']
• Quality [star rating='3.3']
• Value For Money [star rating='3.4']
• Affordability [star rating='4.5']

Here Are Some Other Related Aquarium Hydrometers

2. Bubble Magus Digital Color Screen Salinity Meter

Bubble Magus First Impressions

"Good value."

YOU WILL NOT get an accurate reading if there are bubbles on the needle. Every time I leave to do something I come back and it's at the bottom of my tank. On the shaft of the refractometer, there's a little, rubber-covered nub. However, the numbers are soooo small it is sometimes hard to read. Just rinse with warm water afterwards. I use this for my 10g brackish and it works ok. Bought this as a back up refractometer.

• Bubble Magus Digital Color Screen Salinity Meter
• Manufacture: Bubble Magus

• Editor's Impressions Of The Bubble Magus
• Accuracy [star rating='4.8']
• Quality [star rating='5']
• Value For Money [star rating='4.1']
• Affordability [star rating='4.7']

3. Aquarium Equip UP Glass Saltwater Hydrometer - Reef Soft Coral Salinity Marine Fish Shrimp sea

User Ratings: 55 17

Aquarium Equip D667 UP??????? First Impressions

"No assembly required."

Hate the batteries, but once loaded, it seems to work fine. And it is much more accurate than my old salinity meter. Be sure to buy the calibration solution and test this before use! My only criticism would be that it's a little too dark. It is a little cheaper made but it works great for the cost! It works, we'll i assume it does as i have nothing to compare it to. I was surprise that the product was really cheap compare to the other ones.

• Aquarium Equip UP Glass Saltwater Hydrometer - Reef Soft Coral Salinity Marine Fish Shrimp sea
• 1. Easy to use 2. Green indicators are ideal range of water temperature and specific gravity for most salt water / marine aquariums 3. Hydrometer measures specific gravity 4. Need it for raising brine shrimp
• Manufacture: D667 UP玻璃海水比重計
• Product Dimensions: 0.8 x 0.8 x 6.2 inches; 0.3 Ounces

• Editor's Impressions Of The Aquarium Equip D667 UP???????
• Accuracy [star rating='3.6']
• Quality [star rating='3.6']
• Value For Money [star rating='4']
• Affordability [star rating='4.1']

4. 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']

5. Accurate Automatic Hydrometer Salt Water Salinity Meter Salinimeter for Fish Tank (Square Type)

User Ratings: 63 16

YOSOO123 First Impressions

"Seems to work fine."

It is a little cheaper made but it works great for the cost! Now that it's calibrated I love it! I got this to have a more accurate read than the hydrometer. I decided to upgrade and it was easy to calibrate. I will get one later but for now this will do, since im just starting. Now that it's calibrated I love it! Plus it is super easy to use and clean.

• Accurate Automatic Hydrometer Salt Water Salinity Meter Salinimeter for Fish Tank (Square Type)
• 15 centimeters (6 inches) from the bottom of the water to avoid the error caused by the oil film on the water.
• Keeping your hands clean and can prevent pollution of water from the fish pond.
• It is easy to read and the precision can be + (-) 0.001 units of specific gravity. Professional design make it able to get accurate reading when the temperature of the fishpond is at 18 degrees -28 degrees
• Fish pool, both inside and outside the cylinder can be read. The hydrometer that can float on the surface of the water is simple and easy to read.
• The proportion of water sample can be automatically detected. The proportion, salinity and conductivity of sea water are shown once.
• Manufacture: Yosoo123
• Part Number: Yosoo537gtqix12
• Item Weight: 3.24 ounces
• Product Dimensions: 5.51 x 3.54 x 0.79 inches
• Style: Square Type
• Batteries Included?: No
• Batteries Required?: No

• Editor's Impressions Of The YOSOO123
• Accuracy [star rating='4.2']
• Quality [star rating='4.4']
• Value For Money [star rating='3.4']
• Affordability [star rating='4.5']

6. 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']

7. Kocome Marine Hydrometer Reef Fish Tank Aquarium Water Salinity Specific Gravity Tester

User Ratings: 71

Kocome First Impressions

"Great kit."

I use this for my 10g brackish and it works ok. Plus it is super easy to use and clean. I did NOT calibrate, but am getting accurate readings. I needed this product and it is a lot less expensive than the local aquarium store. It's fast, it's tidy, and it's accurate. But with alittle persistance I am able to read it. Don't care much for having to post a review in order to activate warranty.

• Kocome Marine Hydrometer Reef Fish Tank Aquarium Water Salinity Specific Gravity Tester
• Accurate and easy to read.
• Size: 3.54×4.72×0.59in (Approx.).
• Readings are temperature-corrected & accurate to +/- 0. 002 specific gravity units which range from 1. 000 - 1. 030 specific gravity.
• It is optimum to be put into below 6" deep water, so it can avoid the error from the oil slick.
• Perfect for testing both salinity and specific gravity of your brackish and marine tank.
• Manufacture: KOCOME

• Editor's Impressions Of The Kocome
• Accuracy [star rating='3.6']
• Quality [star rating='4.2']
• Value For Money [star rating='4']
• Affordability [star rating='3.9']

8. TRZ Salinity Refractometer for Aquariums, Marine Monitoring, Saltwater Testing, Dual Sacle 0-100ppt ...

User Ratings: 58 7

TRZ Hamh Optics&Tools First Impressions

"Using for my Pacman frog."

Plus it is super easy to use and clean. Very quick to calibrate and to use. I bought this refractometer as a more accurate option for salinity than a hydrometer. It works, we'll i assume it does as i have nothing to compare it to. I think those reviews just didn't know how to use it properly. Do not spend money on calibration fluid to calibrate this meter. I've tried several different refractometers now and they are mostly the same.

• TRZ Salinity Refractometer for Aquariums, Marine Monitoring, Saltwater Testing, Dual Sacle 0-100ppt Salinity & 1.000-1.070 Specific Gravity Automatic Temperature Compensation.
• It is more accurate than a hydrometer and easy to measure. Designed for the testing the concentration of salt water and brine, perfect for use with aquarium Marine monitoring and quality control in scientific research and clinical laboratories
• Measurement range: Salinity 0 - 100 ppt, (0 - 10% salt content), SG 1.000 to 1.070 SG, Resolution: Salinity +/-1 ppt; +/-0.001 SG
• Easy to use. Place 2 drops sample on the main Prism and close the panel and hold the refractometer up to the light and look through the eyepiece.
• The refractometer's body and the retaining ring are made of brass and chrome plated. The internal optical lens with high refractive index make up the precision optical system.
• Please ignore reviews from Diver. This commentator has a suspicion of being hired. Seller opponents use unfair means to compete！
• Manufacture: Hamh Optics&Tools
• Item Weight: 5.6 ounces
• Product Dimensions: 7.48 x 2.17 x 1.38 inches

• Editor's Impressions Of The TRZ Hamh Optics&Tools
• Accuracy [star rating='3.3']
• Quality [star rating='4.6']
• Value For Money [star rating='5']
• Affordability [star rating='4.1']

9. NEW RHS-10ATC 0-10% Salinity Refractometer Salt Water Aquarium

User Ratings: 53 7

Ade Advanced Optics RHS-10ATC First Impressions

"So, it does seem to work."

Definitely a lot cheaper than a refractometer. I bought this refractometer as a more accurate option for salinity than a hydrometer. But there are some ways to keep on getting accurate readings. I bought this salinity meter for my aquarium. Small problem with bubbles on the needle but other than that no issues. The reading is big enough for you to read and it comes with the batteries. I don't know if that's a positive or negative but just different.

• NEW RHS-10ATC 0-10% Salinity Refractometer Salt Water Aquarium
• Manufacture: Ade Advanced Optics®

• Editor's Impressions Of The Ade Advanced Optics RHS-10ATC
• Accuracy [star rating='3.1']
• Quality [star rating='4.8']
• Value For Money [star rating='3.9']
• Affordability [star rating='3.1']

10. AUTOUTLET Salinity Refractometer for Aquarium Salinity Tester with ATC and Dual Scale 0-100‰ & 1.0...

User Ratings: 89

AUTOUTLET First Impressions

"Better than nothing."

027, I'm so glad I bought this one and it came spot on. Then I made a mark on it to set the salinity of my fish tank. Once I adjusted the refractometer, my aquarium salinity read 1. If you let it sit in the tank overnight, it definitely gives an accurate reading. It's a basic but reliable refractomer I use it for my aquariums. I think those reviews just didn't know how to use it properly. Used distilled water to calibrate, the screw is located under the rubber cap.

• AUTOUTLET Salinity Refractometer for Aquarium Salinity Tester with ATC and Dual Scale 0-100‰ & 1.000-1.070 Specific Gravity Saltwater Tester for Seawater Pool Fish Tank
• Dual scale display provides readings of one-thousandth (0-100PPT) and specific gravity (1.000 to 1.070 SG), and replace the hydrometer for easier and more accurate measurement.
• Automatic temperature compensation. With the help of the ATC function, the salt water tester can automatically compensate for changes in the ambient temperature, which can obtain accurate readings faster and more easily.
• Durable and portable, the salt water tester is made of non-staining, non-corrosive and non-reactive aluminum material, with superb technology, strong and durable, light weight and easy to carry.
• Widely used, can be used for aquarium, marine monitoring, agriculture, horticulture and educational purposes (biological projects).
• Easy to use, salinity refractometer is easy to operate, only 2 drops of sample after calibration can get accurate reading through eyepiece.
• Due to the difference of human focal lengths,when during adjusting, you may just need to rotate in reverse or re-adjust the distance between your eye and the eyepiece.
• It's necessary to keep the surrounding environment with sufficient brightness and suitable temperature during use. Generally,there is no error in the temperature between 10℃-30℃.(50℉-86℉)
• Specific Gravity (D 20/20) and parts per thousand and replaces your poor quality and difficult to read hydrometer.
• Manufacture: AUTOUTLET

• Editor's Impressions Of The AUTOUTLET
• Accuracy [star rating='4']
• Quality [star rating='4.3']
• Value For Money [star rating='5']
• Affordability [star rating='5']