Best Aquarium pH Tester: pH Test Kits, Digital Tester & More

Depending on the species of fish and plants you plan to host in your aquarium, each will have its own unique requirements when it comes to water quality.

You want to create the best home for your aquatic pets, so keeping informed about water quality requirements is important. This will increase the longevity of your pets and keep them healthy and avoid disease.

As you regularly maintain your aquarium, you’ll want to check values such as water hardness, temperature, and pH. pH and devices that measure pH will be the main feature of this article.

We will dive into the best aquarium pH testers currently on the market and provide in-depth reviews and information for deciding which device will suit your needs.

best aquarium ph tester
aquarium ph tester

First, let’s consider why it is important to monitor aquarium pH levels.

The pH scale is quite straightforward to understand: it ranges from 0 to 14, with 0 – 7 considered acidic and 7 – 14 considered basic (also referred to as alkaline).

If you want to get more technical, it is a direct measure of the concentration of hydrogen ions compared with hydroxide ions. A neutral pH, for example, would have an equal concentration of hydrogen and hydroxide ions in the solution.

So why does it matter to a fish? Because water is a medium that is characterized by different pH levels depending on where its found. Fish (and any living creature for that matter) thrive in stable environments, so if you own a fish that is typically used to a certain pH range in the wild, then you will want to replicate that same pH level in your aquarium in order to maintain an equilibrium within the fish and the aquarium.

Extreme pH levels will throw a fish’s system out of balance, which could trigger stress, induce disease, and negatively affect the health of the fish and its surroundings.

In short, if you want happy fish and plants and want them to live a long time, then make sure they live in a stable environment: find their appropriate pH range and stick to that. Good water quality means healthy fish.

What is the Best Aquarium pH Tester

Now, let’s review some of the best aquarium pH testers on the market.

Digital Aquarium Water Tester

The following list mentions our pick for the top three best digital aquarium water testers. Digital aquarium testers work electronically and are reliable and easy to use.        

The Apera Instruments Pen Tester Kit

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  • It is the smallest pH and can reliably test any liquid
  • ±0.01 pH accuracy; Automatic 3-point calibration; 0-60˚C Automatic Temp. Compensation
  • It has a replaceable tube that is great for test tube testing
  • According to Apera’s website, the pen’s following smart functions include:
    • switch from ˚F to ˚C
    • automatic power-off
    • pH probe invalidation reminder (remind you to replace the probe for better performance)


Apera Instruments creates some pretty high-quality performance meters; this small pH meter is no exception.

The pen tester kit comes with 3 types of premixed solutions for various water testing needs and also comes with a portable case to keep the pen and solutions all in one place. Batteries are included. This might not be as important for aquarium testing as all that is really needed is the aquarium water for testing.

It measures several different water parameters but includes salinity which is excellent for this that carry marine fish tanks.

The easy-to-read LCD screen makes viewing a breeze, and the tester shows a smiley face when it’s ready to be used for measuring. We like it because it proves reliable and accurate measurements up to 0.01 pH resolution.

One downside is that the aquarium pen tester is expensive.

The Bluelab pH Pen

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  • Fully waterproof
  • Simple two-point calibration process for quick setup 
  • Automatic temperature compensation for accurate readings everywhere 
  • Double-junction probe for superior accuracy
  • Auto-off function and low battery warning


Bluelab is an established technology company that creates products suited towards growing plants.  They’ve been in business for over 30 years and provide excellent quality products.

The pen has many unique features, but probably the most useful are the temperature gauge, auto-off function, and hold reading function. A hold feature lets us stick our hands into the water, wait a few seconds, and pull it back up.

Calibrating the pen is pretty easy. According to the manufacturer, you would follow these steps:

  1. Soak your probe for 24 hours before you calibrate it
  2. Place the probe in neutral pH water
  3. Press the calibrate button until CAL appears
  4. Rinse off the pro-and place it in pH 4.0 water
  5. Press the calibrate button until CAL appears

We love this pen because it is a hassle-free, simple-to-use pen that provides accurate readings.

We think it’s worth the investment because the pen will last long, provided it’s well taken care of.

One thing to note is that this pen requires it to be “hydrated” every 30 days, which means calibrating the sensor. If you use it regularly, then this might be something you’ll want to consider adding to your aquarium maintenance schedule.

The Roulan pH Tester Pen

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  • Least expensive on this list
  • Small mini-sized ph meter designed to go anywhere.
  • Can be used to test drinking water, swimming pools, PH balance in aquariums, RO system, spa or hydroponics. Basically all the environments that need to test PH value can use this tester to get accurate data. 
  • Easy to use – turn on the switch,put the probe into the water and stir (make the small glass ball fully contact the liquid) and the value can be read when the value is stable. 
  • Automatic temperature compensation


Ruolan’s tester pen is currently the number 1 rated pen in Lab pH meters. It is also the cheapest on this list which is why it is included on here.

If you are looking for a no hassle and straightforward pH tester, at the lowest price point, then you will want to look into this pH tester pen.

Some user reviews mention that this pen can be a hassle because it requires cleaning between every use to keep it functioning properly. However, the trade-off is that you get a pen that is simple to use.

The pen is easy to use. These are the instructions straight from the manufacturer:

  1. Take off the pen cover and clean the electrode with pure water
  2. Put the pen probe into the solution, taking care not to exceed the water level
  3. Turn on the switch, stir gently, and wait for the reading to stabilize
  4. After the reading is stable, read the displayed value
  5. After the test, clean the electrode with pure water, dry the water on the pen tip in time, and cover the pen cover back

The website does mention some troubleshooting tips that make you aware of some potential problems you may run into when using this device:

  • When the PH meter is turned on in the air, the value jumps irregularly, which is a normal phenomenon. The value in the air cannot be used as a reference.
  • When measuring the water with the PH meter, it needs to be stirred gently (to remove the bubbles attached to the probe), and it takes a period of stabilization. It is normal for the value to jump up or down during the test. Please do not just insert it and read it immediately.
  • White crystalline salt appears around the electrode of the PH meter, which is a normal phenomenon of the PH electrode, and the electrode can be removed by immersing it in water and cleaning.
  • The PH meter electrode is made of glass, which is fragile. Please do not drop it or touch it with your hands. Do not test the water above 50℃. Do not test the strong acid and alkali, which will cause the electrode glass to burst.

Overall, it does what you need it to do without breaking the bank but it may require some extra attention in the long run.

Aquarium pH Test Strips

If you do not want a digital reader, then consider aquarium pH test strips. They are easy to use but have a few drawbacks. They work by measuring multiple parameters at a time on one strip with a simple plunge into the water. They test multiple parameters at once but can sometimes be unreliable and expensive if tested in large quantities over time.

Here is our pick for the top aquarium pH test strips:

API 5-in-1 Test Strips Freshwater and Saltwater Aquarium Test Strips

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  • Available in 4, 25, or 100-count boxes
  • Able to monitor pH, NO2, NO3, KH, and GH
  • Works for freshwater and saltwater aquariums
  • Very easy to use


This is one of the easiest ways to test your aquarium water. All you need to do is to simply dip the test strip in your aquarium water and read the results.

It has the ability to test pH, NO2, NO3, KH, and GH with a single test strip. This makes the testing process very simple and efficient.

How to Test Aquarium Water – Easiest Method

Aquarium pH Test Kit

Finally, we will go over Aquarium pH Test Kits which are useful because they provide high accuracy while giving you a variety of testing solutions when you want to test instead of being forced to test for all parameters like the previously mentioned test strips. 

API makes excellent test kits. We will go over three main types including:

  • APT Freshwater Master Test Kit
  • APT Saltwater Master Test Kit
  • APT Reef Master Test Kit

The master test kits work by mixing their chemicals in test tubes along with the aquarium water from your tank. Then you wait for a period of time for the color of the liquid to change and then you compare the corresponding color with a color swatch on the included color chart to determine your specific water parameter.

API Freshwater Master Test Kit

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According to the manufacturer, the API Freshwater Master Kit can test for the following:

  • pH (from 6.0 to 7.6)
  • High range PH (from 7.4 to 8.0)
  • Ammonia: The test results range from 0 ppm (parts per million) to 8.0 ppm.
  • Nitrite: The test results range from 0 ppm to 5.0 ppm.
  • Nitrate: The test results range from 0 ppm to 160 ppm

Inside the test kit, you will find 4 mixing test tubes. This is where you perform the tests. They also come with included caps. Seven individual bottles are included for the various fluids that are used for testing. You also get instructions, the results color chart, and a handy container that keeps it all together.  The container also holds the test tubes upright for you while you perform the testing.

Most customers rave about this test kit because of its high quality and API customer service.

API Saltwater Master Test Kit

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According to the manufacturer, the API Saltwater Master Kit can test for:

  • pH
  • Ammonia
  • Nitrite
  • Nitrate : 

The testing is similar to the freshwater kit in terms of contents and usage but measures specific qualities for saltwater tanks that are important for a healthy tank.

The manufacturer mentions that each kit can be used for up to 500 tests, which would last a year under normal use.

API Reef Master Test Kit

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For the Reef Master Kit the testing is similar per the manufactures website the kit measure:

  • calcium, carbonate hardness, phosphate and nitrate.
  • Comes with 4 different tests calibrated specifically for reef aquariums, 4 test tubes, a tray, and an easy-to-read color card for clear results.
  • Helps protect reef dwellers from dangerous water conditions.
  • High nitrate levels from fish waste and organic compounds can cause fish disease and algae blooms.
  • Easy to use—fill the test tubes, add the test drops and compare results to the color card.

Most customers rave about this test kit because of the high quality and API customer service. However some mention that these kits can sit on shelves for long periods of time and therefore the quality of the chemicals decrease over time. Try to get the newest products available and check the expiration date if applicable.

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