The 16 Best Aquarium Water Test Kits to Help Maintain Healthy Aquatic Life

Best Overall

API Freshwater Master Test Kit

$36 at Amazon $36 at Chewy $36 at Walmart

The API Freshwater Master Test Kit is the best overall test kit for home hobbyists. It's the one I recommend to all our clients due to its accessibility, low price point, and easy-to-understand results. It has everything to test all of your main water quality, including at least 100 tests per testing parameter, seven reagent bottles, four glass tubes with caps, instructions, a color meter chart, and a case to hold everything with slots to keep your glass vials safe and upright. It can take a little bit of practice to use it correctly, but the results are reliable and well worth the effort so long as you read the instructions carefully and shake all of your reagent bottles thoroughly.

The biggest issue with this test kit is that some people struggle to differentiate the colors, especially for the nitrate test, so for best results, we recommend holding your test tube and color result gradient up to a white piece of paper in sunlight. Given its limitations, we also have had a few issues with high false positive results from the nitrate test, so we recommend swapping it out for the nitrate test listed below.

There is also some confusion over the high- and low-range pH tests. If your pH test using the high range is at the very lowest reading, repeat with the other pH test. If your pH is at the high range of the low-range test, repeat with the high range.

_{Testing Parameters: Ammonia, nitrite, nitrate, high- and low-range pH}

Recommended on Reddit

Bluelab Conductivity Pen

$89 $80 at Amazon

While our best overall pick, the API Master Kit, is a great all-in-one option to help you maintain good water quality and healthy aquatic life, it doesn't hurt to supplement it with another tool, like a pH pen. One user in the aquaponics forum on Reddit recommends using the Blueland Conductivity Pen in conjunction with the API Master Kit, which allowed them "to instantly and accurately check pH, temps, and monitor TDS (total dissolved solids) and keep track of TDS creep."

It has ATC (automatic temperature compensation), so readings are accurate and consistent regardless of temperature fluctuations. The large flat electrodes make it easier to clean regularly, which helps prolong the lifespan of the probe. While the pen is "factory-calibrated," it doesn't include a calibration solution, which is an optional add-on despite being a necessity according to many users.

_{Testing Parameters: pH, temperature, TDS}

Best Saltwater

Red Sea Reef Foundation Test Kit

$61 at Amazon View on Bulkreefsupply.com

The Red Sea Reef Foundation Test Kit specifically tests calcium, magnesium, and carbonate alkalinity, essential building blocks for corals and invertebrates. Each test kit contains enough materials to do at least 75 tests per reagent with easy-to-follow instructions and very helpful picture diagrams.

This kit does not include basic parameters, but by combining it with our top pick, you will have a complete kit for any saltwater system at a very affordable price. There is a little bit more effort involved with this test kit due to the additional equipment and length of testing, but the results are well worth the effort.

_{Testing Parameters: Calcium, magnesium, carbonate alkalinity (KH)}

Best Ammonia

Monitor Ammonia Test Kit

$15 at Amazon

Testing for ammonia levels in your aquarium is an essential test whenever you are starting a new system, adding new fish, changing your filtration components, or varying a diet. The Monitor Ammonia Test Kit is very similar to other test kits (including the API Ammonia Test we previously recommended), with two reagents being added to a small sample. What makes this kit better is the colorimetric wheel—so rather than reading a test sideways, this ammonia test kit reads from the top down, allowing for easier color differentiation.

Unfortunately, this test is still limited by its wide-range results, reading from 0 mg/L to 0.25 mg/L to 0.5 mg/L without any range in between. All the equipment is included in this inexpensive test kit for 150 water tests.

_{Testing Parameters: Ammonia}

Best Nitrate

NYOS Nitrate Test Kit

$35 at Amazon View on Bulkreefsupply.com

Nitrate test kits are the one kit that all established tanks require, and the NYOS Nitrate Test Kit provides the easiest-to-read and reliable results for both freshwater and saltwater systems. Other test kits on the market can be very difficult to read with fiddly instructions and reagents. Although this test kit has multiple steps, the results are worth it.

The NYOS test kit is more expensive than other singular test kits (like the Salifert test we recommended previously) and can be more difficult to track down. Although marketed for saltwater, you can use this test kit in freshwater and brackish systems as well. Read the instructions carefully and be sure to use natural light to read the colorimetric chart.

_{Testing Parameters: Nitrate}

Best Nitrite

Monitor Nitrite Test Kit

$10 at Amazon

Nitrite, the middle of your nitrogen cycle and the cause of brown blood disease, can be easily tested with the Monitor Nitrite Test Kit. For most established tanks, you will not need to worry about your nitrite, but for new tanks or those with new fish, components, or a diet change, nitrite testing is critical. This test wins out over the one in the all-in-one kit since it has a more sensitive and smaller range of results (down to 0.1 mg/L over 0.25 mg/L), plus an easy-to-use colorimetric wheel that allows reading from above, rather than the side, making easier to differentiate between colors.

As with all test kits, this one takes a bit of practice to perfect. This test kit can be a little bit hard to find, but you should not need it for the long term; just enough to get your tank cycling correctly. In this kit, everything is included to run 200 tests, so it should easily last for a year of tests before requiring replacement.

_{Testing Parameters: Nitrite}

Best pH

Sera pH Test Kit

$13 at Amazon

The Sera pH test kit can test aquarium pH from 4.5 all the way up to 9.0, providing a great reference range for aquariums struggling with pH problems. The kit provides 100 tests for both marine and freshwater systems using one simple reagent for instant results. This is a great basic test pH test kit for all fish systems, but if you have finicky corals or saltwater fishes, you will likely need a smaller range with shorter increments between results to really narrow down your exact pH.

Inexpensive and easy to use, the Sera pH test kit is a great addition to all aquarium test kit collections. pH is one of the most important aspects of water quality as each species has its own tolerances and consistency is key. If you are having issues with your pH you should move on to the next category, KH or carbonate alkalinity, to help you determine the source of your issues.

_{Testing Parameters: pH (wide range)}

Best KH/GH

API GH & KH Test Kit

$17 $12 at Amazon $10 at Chewy $12 at PetSmart

The API GH & KH test kit is a necessary add-on to any pH test kit. If your KH is out of range, your pH will be as well. The API GH & KH test kit will test both total hardness (GH) and carbonate alkalinity (KH) and will work in both freshwater and marine systems. The kit includes all of the vials and reagents necessary, but total tests will vary depending on how fast you use the reagents.

This is a highly recommended addition to any test kit setup because it's easy to use, cheap, and readily available—however, the biggest complaint with this system is that it measures KH and GH in dKH and dGH, which can be confusing to interpret. By simply multiplying your drop results by 17.1 mg/L you will have a number in ppm, an easier metric to wrap your mind around. Also, our clients have issues with the ”blue to yellow” color conversion; the correct term should be "light yellow," rather than the yellow on the side of the box.

_{Testing Parameters: Carbonate alkalinity (KH), total hardness (GH)}

Best Oxygen

Monitor Dissolved Oxygen Test Kit

$13 at Amazon

The Monitor Dissolved Oxygen test kit provides 60 tests with a range from 0 to 15 ppm down to 0.5 ppm, making it a very specific test kit. This is an excellent test for looking at lower oxygen levels, which can happen as tank temperatures warm or equipment is swapped out. There are many reagents involved and multiple steps, so take your time and read the instructions carefully.

Oxygen levels are critical for your fish and invertebrates and can be easily tested by an electronic probe or test kit, though electronic probes tend to be more expensive and require regular calibration. Most aquariums running any sort of filtration will have sufficient oxygen levels, so if your fish are up and swimming, you probably do not need an oxygen test. If you have lots of plants or algae in your system, you will need to test your oxygen levels at their lowest level before the lights come on or the sun comes up!

_{Testing Parameters: Dissolved oxygen}

Best Phosphate

NYOS Phosphate Reefer Aquarium Test Kit

$32 at Amazon

Phosphate may not affect your fish’s health, but it can be a cause of serious algae problems in freshwater and saltwater systems, so if you have issues battling algae, testing your nitrate and phosphate levels is critical. The NYOS Phosphate test kit is a little bit tricky, with multiple steps, but will give you specific phosphate levels and help you detect smaller trends over time. This is an ideal test kit for detecting small amounts of phosphate and truly getting in control of your levels.

The NYOS Phosphate test kit has a handy colorimetric chart to match up your chosen sample and includes all the equipment required to run 50 tests. If you are having difficulty with high phosphate levels, you should check out our product recommendations for lowering your phosphate levels.

_{Testing Parameters: Phosphate}

Best Copper

API Copper Test Kit

$18 $13 at Amazon $13 at Chewy $14 at Walmart

Whether you’re treating your system for parasites, have an outdoor system, or have old copper pipes, monitoring your copper level is critical to ensuring the health of your fish. At low levels, copper can be toxic, cause secondary illness by weakening the immune system, and crash your pH. To ensure correct copper levels, we recommend the inexpensive API Copper Test kit for use in all aquariums to ensure your fish stays healthy through treatment or plumbing changes.

The API Copper test kit includes reagents for 90 tests and can detect copper levels from 0-4 ppm. Reference ranges are a little broad in the results, so ask your veterinarian for the specific level to test for before adding copper as a parasite treatment, as well as test your carbonate alkalinity (KH). Since the results are in circles, rather than bars, we recommend removing the cap after your testing procedure and reading results from above.

_{Testing Parameters: Copper}

Best Salinity

AquaticHI Aquarium Refractometer

$28 at Amazon

Although there is no “test kit” for salinity, there is a very reliable way to get a good handle on your salt levels to ensure your saltwater or brackish system is within range, and that is by using the AquaticHI Aquarium Refractometer. An essential tool for any saltwater aquarium owner, a refractometer is a simple tool that can read salinity instantly using only a drop of water. Take good care of yours and it will last your lifetime! (Our mobile office has used this exact model for over 10 years.)

The AquaticHI Aquarium Refractometer comes in its own hard case with all the tools needed for correct operation and storage. The biggest issues with using a refractometer are user error, such as not putting enough water on, closing the cover too hard, and having to read VERY small numbers. You can change the focus by twisting the eyepiece, so get those reading glasses out before you attempt a reading.

_{Testing Parameters: Salinity, specific gravity}

Best Low-Range Salinity

eSeasonGear Salt Meter

$67 at Amazon.ca

For low-range salinity (up to 10 ppt), we recommend the eSeasonGear Salt Meter, a model we've used for many years and recommend to all of our clients using low levels of salt. Salt can be a great treatment for many common fish issues, and this low-cost probe can detect smaller levels that can be hard to read on the refractometer.

The biggest complaint with this probe is reading the results, as it reads levels in ppm, a small “x10” will appear in the upper right corner when converting to ppt. It is very small and easily missed, but the probe also has a “hold” function that will keep the reading present on the screen so it can be removed for closer reading. I have found these probes last about 10-12 months before they need to be replaced since they cannot be calibrated, however, it's well worth it for the low price.

_{Testing Parameters: Salinity}

Best for Carbon Dioxide and Planted Aquariums

Clscea Aquarium CO2 Acrylic Drop Checker

$12 at Amazon

If you are using carbon dioxide to grow a planted tank, you will need to be able to test your levels to ensure your plants are not getting too much CO2 and your fish isn't being exposed to toxic levels. There are many internal carbon dioxide detectors that rely on your tank’s pH to indicate an appropriate level of CO2 for your tank, and our favorite is the aesthetically pleasing Clscea Aquarium CO2 Acrylic Drop Checker. Rather than a paper range, a colorimetric drop is placed within the device itself for easy monitoring and instantaneous, reliable results.

These carbon dioxide devices can be slightly tricky to install and will need their reagent changed occasionally, but the Clscea Aquarium CO2 system is very easy to use, even for beginners. As you note the color change in the device, you can increase or decrease your carbon dioxide to keep your pH exactly in your plants’ range.

_{Testing Parameters: pH}

Best for Continuous Monitoring

Yewhick Aquarium monitor

$96 $76 at Amazon

Rather than test on a daily or weekly basis, track your pH, salinity, and temperature readings in real time with the Yewhick Aquarium Monitor. This system can connect directly to your phone, set up alarms, and trigger any backup systems depending on how it is set up. Although it only tests a few parameters (pH, salinity, and temperature), these levels can be critical to the health of your fish in both indoor tanks and outdoor ponds. 

As with any continuous monitoring system, you will need to calibrate the system over time. This is the case for all quality digital probes and should not be skipped. This product includes full instructions and reagents for calibrating correctly for accurate results.  

 _{Testing Parameters: pH, salinity, temperature}

Best Temperature

Marina Floating Thermometer with Suction Cup

$10 $8 at Amazon $6 at Chewy

There are many fancy electronic probes and infrared thermometers for checking a tank's temperature, but we have found that the simplest method is best. The Marina floating thermometer can be used in any system and provides reliable and accurate results without any calibration. The biggest issue with this thermometer is the smaller print numbers.

A thermometer is an essential tool for all aquariums and ponds. You should always have one in your system to keep a close eye on your water temperature. For larger systems, such as outdoor ponds, you can substitute this pool/spa model to allow for easier reading. 

_{Testing Parameters: Temperature}