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
  • 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)

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
  • Quality
  • Value For Money
  • Affordability

KKmoon Final Thoughts

"This tool is AMAZING!"

The refractor was off out off the box. I have a 2000+ gallon pond and I just put salt in it last month. Clear readout with the ability to calibrate and focus. I've tried several different refractometers now and they are mostly the same. He is too cute not to want to take care of properly. When I saw the price offered on this one, I decided to buy and I love it. Very easy, turn screw very slowly to calibrate.

Overall Score
4.2


(18 Points)

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
  • Quality
  • Value For Money
  • Affordability

Hongzer Final Thoughts

"So far so good."

It is a little cheaper made but it works great for the cost! Pretty darn accurate for the price. Ambient room light at night is not enough and makes what you're viewing dark. Normally that gives the more accurate reading. Now its easy to make sure I have the correct amount of salt in my aquariums. I was surprise that the product was really cheap compare to the other ones. This refractor should last a good number of years.

Overall Score
5.0


(2 Points)

4. 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
  • Quality
  • Value For Money
  • Affordability

Kocome Final Thoughts

"026 as expected."

I would recommend you to purchase this and skip the other ones. I have tried others before but this has given me accurate and stable results. On the shaft of the refractometer, there's a little, rubber-covered nub. I couldn't decide between this and one of the float arm meters or both. Very easy, turn screw very slowly to calibrate. Looks to provide very accurate readings. The instant ocean hydrometer will always be right.

Overall Score
4.6


(9 Points)

5. 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
  • Quality
  • Value For Money
  • Affordability

RHINO TECHNOLOGY Final Thoughts

"Other then that."

I tried it over and over and no bubbles! I don't know if that's a positive or negative but just different. 027, I'm so glad I bought this one and it came spot on. I got this to have a more accurate read than the hydrometer. Looks to provide very accurate readings. I will get one later but for now this will do, since im just starting. And it is much more accurate than my old salinity meter.

Overall Score
5.0


(8 Points)

6. UEETEK Heavy Duty Submersible Pump for Aquarium,Powerhead Fountain Water Hydroponic Pump with US-plu...

User Ratings: 51 49

UEETEK First Impressions

"Other then that."

Just give me one simple, accurate reading to go by, and I'm happy. Make sure to knock out the bubbles on the white dial by hitting it with your knuckle. Comes with a nice carrying case for easy and secure transportation. Does just as good of a job of any meter you would buy at the store! This is perfect to keep a check on the salt level in your tank. Small problem with bubbles on the needle but other than that no issues. Very easy, turn screw very slowly to calibrate.

  • UEETEK Heavy Duty Submersible Pump for Aquarium,Powerhead Fountain Water Hydroponic Pump with US-plug for Fish Tank,2.3 x 1.7 x 2.0 inch (L x W x H)
  • This submersible pump is designed for reliability and ultra-quiet operation.
  • Small size, high efficiency, low consumption, low noise.
  • Suction cups to fit vertical or horizontal mounting.
  • Suitable for use in hydroponic systems, ponds, fresh and saltwater aquariums, fountains and filter systems.
  • Note: The item is with US plug adapter:NLY for 110V, NOT for 220V. Please confirm the voltage of your area before placing an order.
  • Manufacture: UEETEK
  • Product Dimensions: 2.28 x 1.65 x 1.97 inches; 7.41 Ounces
  • Editor's Impressions Of The UEETEK
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

UEETEK Final Thoughts

"Nice product!"

So once your instant ocean shows a measurement. When I saw the price offered on this one, I decided to buy and I love it. There are conversion charts and tables online. Make sure to knock out the bubbles on the white dial by hitting it with your knuckle. Small problem with bubbles on the needle but other than that no issues. Like that it comes with everything needed. Don't spend your money on calibration solution.

Overall Score
3.1


(3 Points)

7. RZ Aquariums Salinity Refractometer for Seawater Marine Fish-Keeping, Dual Scales Specific Gravity S...

User Ratings: 74 3

RZ First Impressions

"Great product."

I bought this salinity meter for my aquarium. I needed this product and it is a lot less expensive than the local aquarium store. When I saw the price offered on this one, I decided to buy and I love it. Works well on my Saltwater Aquarium. I was surprise that the product was really cheap compare to the other ones. But there are some ways to keep on getting accurate readings. Too that makes it appear too cheap.

  • RZ Aquariums Salinity Refractometer for Seawater Marine Fish-Keeping, Dual Scales Specific Gravity Salinity Meter Hydrometer 0-100ppt & 1.000-1.070, Saltwater Tester with ATC Function
  • Measures on 2 Scales: Aquariums refractometer features Specific Gravity (D 20/20) 1.000-1.070sg and parts per thousand 0-100PPT (1‰=1ppt=1000ppm)
  • Seawater refractometer measures saltwater or salinity of water, ideal for aquarium, marine monitoring, fish-keeping,salty pools&spas and etc.
  • ATC Function: salty water refractometer with automatic temperature compensation, allow you obtain accurate readings easier and faster
  • Salinity Refractometer is made of aluminum body and ABS rubber light and very sturdy, comes with a hard plastic case, a mini screwdriver, a dropper
  • Easy to Use: put 2-3 drops on the saltwater’s prism, towards light then to get the accurate readings through the optic eyepiece, ideal for replacement the poor quality and difficult to read hydrometer refractometer
  • Manufacture: RZ
  • Editor's Impressions Of The RZ
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

RZ Final Thoughts

"Seems to work fine."

I will get one later but for now this will do, since im just starting. Comes with a nice carrying case for easy and secure transportation. I decided to upgrade and it was easy to calibrate. Plenty of info on YouTube and the web if you don't know how. 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. Be sure to adjust the focus by turning the eye focal when you first receive.

Overall Score
4.6


(296 Points)

8. 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
  • Quality
  • Value For Money
  • Affordability

YOSOO123 Final Thoughts

"0, it reads 1."

I use this for my 10g brackish and it works ok. I have purchased before will buy again! Would be nice if stem were slightly larger for easier read. I have gone two years in this hobby with a hydrometer. It is easy to read and perform the procedure in seconds. Ambient room light at night is not enough and makes what you're viewing dark. I have a 2000+ gallon pond and I just put salt in it last month.

Overall Score
4.0


(13 Points)

9. 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
  • Quality
  • Value For Money
  • Affordability

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


(57 Points)

10. Eyourlife Salinity Refractomer Aquarium Optical Optics Refractometer with Auto Temperature Compensat...

User Ratings: 64 8

Eyourlife First Impressions

"So easy to use."

Great tool if you have a salt-water fish tank or a decorative pond. Ultimately, the measurement was exactly the same as our old tester. I have purchased before will buy again! Great product I used for beer making and my saltwater aquarium. I would suggest purchasing the salt calibration solution. I tried it over and over and no bubbles! Very quick to calibrate and to use.

  • Eyourlife Salinity Refractomer Aquarium Optical Optics Refractometer with Auto Temperature Compensation ATC Digital Dual Scale Salinity Meter Hydrometer Specific Gravity for Saltwater Seawater Marine
  • SALINITY REFRACTOMETER for measuring the salinity of salt water quickly and accurately, ideal for agriculture, industry and research application, such as Mariculture, Fish Culture, Aquarium, Marine Survey, Water Quality Monitoring, Salt Production, Manufacture of Normal Saline, Salinity Measurement in Food Processing etc. It can also be used for medical institutions and university research.
  • DUAL SCALES: The Refractometer is a equipment to measure the liquid concentration(the concentration of salt) by using the light, working basis on that the liquid with different concentrations have different light refractive index. The Measures on 2 scales: Specific Gravity (0.001, Range: 1.000 - 1.070, D 20/20,) and Parts Per Thousand (1‰, Range: 0-100‰).
  • ATC FUNCTION: Automatic Temperature Compensation during 10-30℃, eliminating data errors caused by temperature changes and guaranteeing a consistent accurate result.
  • WITH DURABLE STORAGE CASING: With a sturdy and light weighted case, it is very convenient to storage and carry. The body is made of stainless steel and is very durable, the eyepiece is in high quality for better viewing, adopting optical glass lens rather than plastic lens for accurate measurement.
  • PACKAGING: 1 x Salinity Refractometer, 1 Pipette, 1 x Instruction manual, 1 x Mini screwdriver, with a durable storage case.
  • 1 x Salinity Refractometer
  • 1 x Pipette
  • 1 x Instruction Manual
  • Manufacture: Eyourlife
  • Product Dimensions: 7.91 x 2.99 x 2.2 inches; 5.6 Ounces
  • Editor's Impressions Of The Eyourlife
  • Accuracy
  • Quality
  • Value For Money
  • Affordability

Eyourlife Final Thoughts

"And accurate."

I've checked about 5 times with the hydrometer and each time has been near perfect. Great tool if you have a salt-water fish tank or a decorative pond. But there are some ways to keep on getting accurate readings. Pretty darn accurate for the price. So worth it considering its great quality and great price. Does just as good of a job of any meter you would buy at the store! It is a little cheaper made but it works great for the cost!

Overall Score
4.4


(18 Points)

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