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. 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']

3. emours Aquarium Gloves Waterproof Elbow Length Long Sleeve Scratch Resistant Work Gloves 27-Inch

User Ratings: 71 6

emours First Impressions

"Great product."

At first, I was getting bubbles sticking to the rotating arrow. I decided to upgrade and it was easy to calibrate. The water was at what I expected it should be. Pretty darn accurate for the price. I don't want to deal with temperature correction or. Wipe down glass surface to dry it and put it back on the shelf til next time. When I'm testing my aquarium water, I want immediate, clear results.

• emours Aquarium Gloves Waterproof Elbow Length Long Sleeve Scratch Resistant Work Gloves 27-Inch
• Material: Polyvinyl chloride (PVC) + knit cloth; durable
• PVC material is chemical and scratch resistant. With velvet inner, can keep your hand warm even in the cold water environment.
• 27-Inch extra long design. Can keep your hand from getting wet inside the tank .Hand portion size:18x12.5cm/ 7 x 4.9inch ( L x W) ,one size fits most all(medium to large size); with elasticated cuffs, protects hands and arms up to the shoulder;
• Thicken material,fully lined,waterproof. Keep your hands and arm dry when changing fish tank water, also can prevent allergies, cuts during aqua maintenance;
• Multifunctional. Can be used in aquarium cleaning, also can be used in aquatic seafood fishing operations.
• Manufacture: Kensid

• Editor's Impressions Of The emours
• Accuracy [star rating='3.7']
• Quality [star rating='3.5']
• Value For Money [star rating='4.5']
• Affordability [star rating='4.3']

4. 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']

5. Coralife BioCube Mini Aquarium Hydrometer

User Ratings: 37 28

Coralife 100115642 First Impressions

"NO BUBBLES!"

My corals will be much happier now. Every time I leave to do something I come back and it's at the bottom of my tank. And it is much more accurate than my old salinity meter. This device is a godsend and so much easier and cleaner to use. It is a little cheaper made but it works great for the cost! Just give me one simple, accurate reading to go by, and I'm happy. When I saw the price offered on this one, I decided to buy and I love it.

• Coralife BioCube Mini Aquarium Hydrometer
• Can remain submerged inside your aquarium or sump
• Know your salinity in a glance
• Compact design allows for discreet placement in the aquarium
• Ideal for all saltwater aquariums and sumps
• Manufacture: Central Garden & Pet
• Product Dimensions: 3.9 x 1 x 6 inches; 0.8 Ounces

• Editor's Impressions Of The Coralife 100115642
• Accuracy [star rating='3.4']
• Quality [star rating='4.3']
• Value For Money [star rating='2.8']
• Affordability [star rating='3.9']

6. Dr. Marine Saltwater Marine Aquarium Salinity Portable Refractometer Meter ATC 0~10% reef

Aquarium Equip D-803 UP鹽度檢測器 First Impressions

"Great Product, Thanks!"

I bought this and a hydrometer because of the reviews saying its not accurate. Great product I used for beer making and my saltwater aquarium. Bought this one to check my old one, this one checked right on the dot at 1. I needed this product and it is a lot less expensive than the local aquarium store. Simple to use, but if there are any air bubbles the results will be way off. I have purchased before will buy again! Don't spend your money on calibration solution.

• Dr. Marine Saltwater Marine Aquarium Salinity Portable Refractometer Meter ATC 0~10% reef
• This latest salinity refractometer is designed for testing the concentration of salt water and brine and used for quality control in research and clinical laboratories and marine industry. Its scale provides a direct reading of the specific gravity and concentration (Parts per Thousand) of salt in water.
• Manufacture: UP AQUA

• Editor's Impressions Of The Aquarium Equip D-803 UP鹽度檢測器
• Accuracy [star rating='4.1']
• Quality [star rating='5']
• Value For Money [star rating='5']
• Affordability [star rating='4.2']

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. 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']

9. Dual Scale Salinity Refractometer ATC 0-100ppt (0-10%) & 1.000-1.070 Specific Gravity, Portable Mete...

User Ratings: 76 4

Gain Express RES-10ATC First Impressions

"Documentation is limited."

So once your instant ocean shows a measurement. And always make sure there is no bubbles on the measuring unit. Make sure to knock out the bubbles on the white dial by hitting it with your knuckle. But with alittle persistance I am able to read it. Make your own by simply boiling some water and collecting the condensate. Works great,& comes in a storage box. Trying to turn it by hand won't work.

• Dual Scale Salinity Refractometer ATC 0-100ppt (0-10%) & 1.000-1.070 Specific Gravity, Portable Meter Tester for Seawater Salt Sea Water Aquarium Brackish Reef Tank Marine
• Range: 0-100ppt (0-10% Salinity) and Density/ Specific Gravity 1.000-1.070 1ppt Salinity and 0.001 g/cm3 Density Resolutions
• Water or a salt (brine) refractometer preferred by aquarist, it checks saltwater & brine or salinity of water, best for aquariums and marine monitoring
• True seawater or a salt (brine) refractometer preferred by aquarist
• Calibrate simply by distilled water, comes with free screwdriver for calibration
• Has automatic temperature compensation (ATC) and has built with the highest and finest quality of aluminum & rubbe
• Manufacture: Gain Express Holdings Ltd
• Part Number: REB-32ATC
• Material: ABS Material for Handle
• Item Weight: 9.9 ounces
• Color: 0-10% Salinity
• Batteries Included?: No
• Batteries Required?: No

• Editor's Impressions Of The Gain Express RES-10ATC
• Accuracy [star rating='3.6']
• Quality [star rating='5']
• Value For Money [star rating='5']
• Affordability [star rating='4.4']

10. ZRM&E Seawater Hydrometer for Aquarium Aquaculture Seawater Densimeter Ocean Hydrometer Salinity Met...

User Ratings: 70 30

ZRM&E First Impressions

"Gave me confidence."

YOU WILL NOT get an accurate reading if there are bubbles on the needle. I have purchased before will buy again! I felt it wasn't accurate which was verified by my LFS. Very quick to calibrate and to use. It says in the instructions to use distilled water. I bought this refractometer as a more accurate option for salinity than a hydrometer. Don't spend your money on calibration solution.

• ZRM&E Seawater Hydrometer for Aquarium Aquaculture Seawater Densimeter Ocean Hydrometer Salinity Meter for Fish Tank Salinity Specific Gravity Test
• Made of high quality plastic, aquarium transparent, automatic accurate reading brine hydrometer
• Accurate, durable and easy to read salt and specific gravity of your marine aquarium, small and waterproof. If the specific gravity is between 1.000-1.019, it indicates that the specific gravity is low; if the specific gravity is between 1.020-1.023, it indicates that the specific gravity is normal; if the specific gravity is between 1.024-1.030, it indicates that the specific gravity is high
• The external range of the scale indicates salinity (PPT), and the internal range of the scale indicates gravity. And clearly mark the safe area. Application range: 0-40 degrees (1.000-1.030). If the salinity PPT is between 32-40, it indicates that the salinity is high; if the salinity PPT is between 27-31, it indicates that the salinity is normal; if the salinity PPT is between 0-26, it indicates that the salinity hydrometer is low
• Wide range of applications: Suitable for salt water and sea water fish tanks. Perfect for testing salinity and specific gravity of saltwater and seawater tanks, including solubility and specific gravity scales. Suitable for fresh water and sea water
• Easy to read swing arm pointer and ultra wide stable base can provide accurate test results
• Manufacture: DGHP

• Editor's Impressions Of The ZRM&E
• Accuracy [star rating='2.9']
• Quality [star rating='3.8']
• Value For Money [star rating='4']
• Affordability [star rating='3.2']