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']

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

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

2. Aeroway Salinity Refractometer, Aquarium & Seawater - Dual Scale (1.0 to 1.070 S.G.)

User Ratings: 79 3

Aeroway 8541957182 First Impressions

"021 the other read."

Make sure to knock out the bubbles on the white dial by hitting it with your knuckle. Normally that gives the more accurate reading. I will get one later but for now this will do, since im just starting. I run brackish tanks and it works perfectly. I strongly recommend a refractometer vs. This device is a godsend and so much easier and cleaner to use. On the shaft of the refractometer, there's a little, rubber-covered nub.

  • Aeroway Salinity Refractometer, Aquarium & Seawater - Dual Scale (1.0 to 1.070 S.G.)
  • Measure salt water or salinity of water, ideal for aquariums and marine monitoring.
  • Features automatic temperature compensation (ATC),The main part is made of chromium, it's very durable.
  • Measures on 2 scales, Specific Gravity (D 20/20) and parts per thousand (‰).
  • Comes with hard case, dropper, screwdriver and cleaning cloth.
  • We offer premium quality and the best service, no matter what reason cause dissatisfaction,just return it within 30 days for a full refund. No questions asked, no hassle.
  • Manufacture: Aeroway
  • Editor's Impressions Of The Aeroway 8541957182
  • Accuracy [star rating='3.7']
  • Quality [star rating='4.2']
  • Value For Money [star rating='4.9']
  • Affordability [star rating='4.7']

Aeroway 8541957182 Final Thoughts

"Works great!"

Simple to use, but if there are any air bubbles the results will be way off. I compared the readings using this hygrometer and the calibrated refractometer. Normally that gives the more accurate reading. It's a basic but reliable refractomer I use it for my aquariums. Every time I leave to do something I come back and it's at the bottom of my tank. I bought this and a hydrometer because of the reviews saying its not accurate. So worth it considering its great quality and great price.

Overall Score
4.6

[star rating="4.6"]
(43 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. 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 [star rating='5']
  • Quality [star rating='5']
  • Value For Money [star rating='4.8']
  • Affordability [star rating='5']

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

[star rating="4.7"]
(1512 Points)

5. Ade Advanced Optics aaosal Professional Automatic Temperature Compensation Sea Water Salinity Refrac...

User Ratings: 68

Ade Advanced Optics aaosal First Impressions

"What else can I say."

I've tried several different refractometers now and they are mostly the same. When I saw the price offered on this one, I decided to buy and I love it. The refractor was off out off the box. I would suggest purchasing the salt calibration solution. I don't want to deal with temperature correction or. The product itself is very good quality and the included instructions are very clear. Looks to provide very accurate readings.

  • Ade Advanced Optics aaosal Professional Automatic Temperature Compensation Sea Water Salinity Refractometer for Aquarium, Hydrometer, 0-100 ppt and 1.000-1.070 Salinity S.G.
  • Manufacture: Ade Advanced Optics
  • Editor's Impressions Of The Ade Advanced Optics aaosal
  • Accuracy [star rating='3.5']
  • Quality [star rating='5']
  • Value For Money [star rating='4.5']
  • Affordability [star rating='3.6']

Ade Advanced Optics aaosal Final Thoughts

"Arrived quickly."

This requires repeatedly tapping the arm with a pencil. 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. I have tried others before but this has given me accurate and stable results. I would suggest purchasing the salt calibration solution. It's fast, it's tidy, and it's accurate. When I compared it to what my local pet store was reading my water at it was dead on.

Overall Score
4.5

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

6. 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)

7. 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']

Coralife 100115642 Final Thoughts

"I say it works very well."

Waterproof if you accidentally drop it in the pool. Do not spend money on calibration fluid to calibrate this meter. I use this for my 10g brackish and it works ok. I use this for my 10g brackish and it works ok. There are conversion charts and tables online. Wipe down glass surface to dry it and put it back on the shelf til next time. I would recommend you to purchase this and skip the other ones.

Overall Score
3.3

[star rating="3.3"]
(57 Points)

8. Aichose Salinity Refractometer for Seawater and Marine Fishkeeping Aquarium, Saltwater Pool, with AT...

User Ratings: 71

aichose SR0024BE First Impressions

"Easy to use."

I use this for my 10g brackish and it works ok. I was surprise that the product was really cheap compare to the other ones. Make sure to knock out the bubbles on the white dial by hitting it with your knuckle. 010; I can easily read this off of the refractometer. I have a 2000+ gallon pond and I just put salt in it last month. I have a 2000+ gallon pond and I just put salt in it last month. It did not need adjusting to calibrate, though I tried to just to see how it worked.

  • Aichose Salinity Refractometer for Seawater and Marine Fishkeeping Aquarium, Saltwater Pool, with ATC Function, Dual Scale: Salinity 0-100‰ and Corresponding Specific Gravity
  • It is designed for the measurement of seawater or low concentrated saltwater.
  • Dual scale: 0-100‰ salinity and corresponding specific gravity 1.000-1.070
  • Automatic temperature compensation function minimizes the effect of the temperature on testing result.
  • Easy to Use: It's very easy to use even for new users. And no battery needed.
  • Ideal for marine fishkeeping aquarium, saltwater pool, marine monitoring,lab,agricultural, gardening and educational purposes.
  • Manufacture: XDC Co,.Ltd.
  • Editor's Impressions Of The aichose SR0024BE
  • Accuracy [star rating='4.4']
  • Quality [star rating='5']
  • Value For Money [star rating='5']
  • Affordability [star rating='4.3']

aichose SR0024BE Final Thoughts

"Gave me confidence."

I would like to provide a great marine environment for sea-fishes. It's perfectly accurate based on the known calibration fluid. I would suggest purchasing the salt calibration solution. Great little device to check your salt water levels in the swimming pool or spa. A hydrometer for making sure you have the right saltwater mix. I would like to provide a great marine environment for sea-fishes. I bought this and a hydrometer because of the reviews saying its not accurate.

Overall Score
4.5

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

9. 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 [star rating='3.8']
  • Quality [star rating='5']
  • Value For Money [star rating='3.9']
  • Affordability [star rating='4.5']

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

[star rating="4.8"]
(10 Points)

10. 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']

Aquarium Equip D667 UP??????? Final Thoughts

"No assembly required."

I tried it over and over and no bubbles! Easy to use, easy to clean, easy to read. I did NOT calibrate, but am getting accurate readings. Small problem with bubbles on the needle but other than that no issues. Find a good light source to make reading easier. It's a basic but reliable refractomer I use it for my aquariums. This refractor should last a good number of years.

Overall Score
3.8

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

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