Updated 2023
There are three methods to test the salinity of your water:
1. Hygrometer
2. Refractometer
3. Probe
I must mention a fourth, but I don’t recommend the tasting method as it is not accurate!
The most precise and best value, in my opinion, is the refractometer, making it my #1 choice. For under $30, you can measure your aquarium’s salinity for a lifetime. It rarely requires calibration, and with proper cleaning, it can last for years.
If you’re looking to build a saltwater tank on a budget, the hygrometer will suffice as it provides reasonable accuracy.
However, unforeseen accidents can lead to fluctuating salinity levels without your knowledge. In such cases, a salinity probe comes in handy. It may require occasional calibration, but that’s about it.
For those interested in advanced features, the Neptune Apex offers a salinity probe and remote tank monitoring from anywhere in the world. But it comes with a hefty price tag of around $500, so I don’t recommend it for everyone.
5. Coralife Deep Six Hydrometer
Unlike the other items on this list that measure the salinity of water, this hydrometer is designed to measure the specific gravity. To use it, you fill the hydrometer with saltwater, and the plastic dial in the middle will float and indicate a number. Specific gravity measures the density of the water, not the amount of salt.
While it may not be the most accurate method, it is likely to be precise to within 0.001 ppm, which is accurate enough for most practical purposes. For your livestock, consistency is more crucial than an exact number.
Using this hydrometer can be a bit cumbersome, as you have to fill it with water, hold it steadily, empty it, rinse it with freshwater, and allow it to dry. However, it does save some money and gets the job done!
4. Milwaukee Seawater Digital Refractometer
While this option may be a bit pricey, it is undoubtedly one of the most accurate choices available. All you need to do is calibrate it with a bottle of distilled water, and then simply use a pipette to add water into the tester, providing you with an immediate reading.
If you value precision and want the utmost accuracy, this product would be a solid recommendation. It’s user-friendly, easy to clean, and the digital read-out ensures you can confidently obtain the most accurate readings possible.
Operating on the same principle as a hand-held refractometer, it offers the advantage of being easier to read and has a low probability of user error!
3. Hanna Instruments Waterproof Salinity & Temperature Tester
This is actually now my go to tester. It boasts user-friendly features such as easy usage, simple cleaning, and straightforward calibration. Just a quick rinse with RO/DI water after each use, and you’re good to go.
However, there are a couple of drawbacks to consider. Firstly, it requires monthly calibration, which isn’t a major inconvenience, but you’ll need to purchase their calibration packets, which can be somewhat costly at around $1.00 each.
The most significant drawback is that this tester is specifically designed for testing freshly made saltwater, not tank water. While many still use it for aquarium testing, this limitation can affect its accuracy over time. After a month of use, I’ve found that the calibration can be off by 0.002 ppm, which is a significant deviation. So while I do like this item, it may not be the most accurate option available.
That being said, I’ve had no problems with this, and in fact I consistently test fresh made water and tank water, and they are exactly the same!
2. American Marine Pinpoint Salinity Monitor
This salinity monitor is truly impressive. With occasional calibration (once every few months), it can last for years without any issues. The digital display provides a conductivity reading, which can be easily converted to specific gravity using a simple calculator.
However, there are a couple of downsides to consider. First, it’s not waterproof, so handling it with care is essential. The probe is relatively short, which means you might not be able to leave it in your sump and mount the display elsewhere. Additionally, it can only be mounted on a flat surface using velcro.
Overall, this is a great item that offers high accuracy. However, it is on the expensive side. If you’re considering a probe-based option, you might want to save up for a Neptune Apex, which would allow you to monitor your tank continuously.
1. Refractometer
I’ve been using this refractometer for over five years now, and it has been consistently reliable since day one. I calibrated it when I first received it, and even after checking it periodically, it has never shown any deviation.
At such an affordable price, there’s no reason not to get this refractometer. Using it is a breeze – just place a few drops of saltwater on the measuring surface, put down the plastic top, and look through the viewfinder to find the reading.
The best part is, it works flawlessly, and the only maintenance required is to rinse and dry it after each use. It’s that simple.
Out of all the items on this list, if I had to choose one, it would undoubtedly be this refractometer. I wholeheartedly recommend it without any hesitation.
