How to Test the Water in an Aquarium

Ammonia and nitrite imbalances are invisible fish killers that can be kept in check if you test and treat your aquarium water. For healthy, thriving fish, water conditions in the aquarium need to be the same or very similar to those found in nature. Water test results compare your actual water conditions to the ideal conditions in the fish’s natural habitat to show you where correction is needed.

Regular water testing is an essential part of maintaining a healthy aquarium. If you don’t feel comfortable performing your own testing, then simply bring a sample of your aquarium water to your local fish store for testing and guidance. Many stores will offer free water testing or will charge you a nominal fee. Compare their fees with the cost of a DIY test kit for the best deal.

There are three types of aquarium test kits.

  • Test strips – Least accurate and most expensive (per test)
  • Liquid test kits – Accurate and affordable
  • Scientific meters and probes – Precise but expensive

All of these options are accurate enough to maintain your tank but come with their pros and cons.

Test strip kits are the easiest, most convenient to use and most expensive cost per test.

Pros –

  1. It takes less than a minute to test all aquarium water parameters

Cons –

  • Expensive
  • Test strips expire and have unreliable results when they do
  • Results become inaccurate when:
    • Cap is not sealed properly
    • Stored in a hot area above room temperature
    • Exposed to moisture
    • Touching test pads on strip with fingers

Test tube kits use chemical drops, take longer to test, are slightly more accurate than test strips and is the least expensive option.

Pros –

  1. Inexpensive
  2. Easy to use
  3. Reliable results
  4. Comprehensive testing, all in one box

Cons –

  1. Not all kits are ideal for salt and freshwater tanks
  2. Color charts are not standardized making some hard to read

Scientific meters and probes are the absolute best aquarium water testing option available.

Pros –

  1. Incredibly accurate

Cons –

  1. Expensive

Let’s talk about Cost Comparisons

Cost comparison is calculated by factoring the cost of the kit with the total number of tests you can perform. Test strip kits come in packs of 25 to 150 and averages $16.00 for 100, then ammonia test strip kit averages another $15.00. A single test tube dropper kit can provide upwards of 800 tests and averages $30.00 for the kit which includes the ammonia test drops.

Testing your Freshwater or Saltwater Aquarium with Test Strips

Testing your freshwater aquarium water is easiest with a test strip kit. Simply dip and swirl the test strip in the water then compare the colors on the strip to the easy-to-read comparison chart to see pH, nitrite, nitrate carbonate, chlorine, alkalinity and water hardness in freshwater and saltwater aquariums.

Most ammonia test strips are sold separately and also use an easy-to-read color-coded comparison chart to easily see ammonia concentration levels in both salt and freshwater aquariums.

The steps to test your aquarium water are simple:

There are currently no multi-test strips that include tests for ammonia so you will need to purchase two test strip kits.

  • Aquarium water multi-test strip kit
  • Aquarium water ammonia test strip kit

Our top choices for best freshwater and saltwater aquarium test strips are:

The DIP & GO Aquarium Test Strips and Ammonia Test Kit is the best complete “All-in-One” test strip kit on the market.  Reasonably priced with 100 test strips testing general hardness, Alkalinity Carbonate Hardness (KH), pH, Nitrates, Nitrites and chlorine (chlorine and chloramine). The complete test kit also comes with a separate test kit tube with 30 ammonia test strips.

The reason the multi-test strip kit and ammonia test strip kit are in separate containers is because the ammonia testing chemical on the test strips will interfere with the integrity of the chemicals on the 6-in-1 aquarium test strips if they were kept together.

Note: The 6-in-1 aquarium test strip has 100 strips in total, 50 in bottle and another 50 sealed separately in a pouch so you can use it to refill when the strips in the bottle run out. Test strips begin breaking down once exposed to air with a limited expiration date. Keeping the additional 50 strips in the separate sealed pouch extends the overall life of the kit.

Reasonably priced test stripsPricy compared to other testing methods
“All-in-One” kit includes 6 in 1 essential testing parameters and additional ammonia test strips 
Easy to read color guide 
Freshwater and saltwater compatible 

Testing Your Freshwater Aquarium Water with the Test Tube and Liquid Droppers Kit

Testing your freshwater aquarium water with test tubes and droppers is simple. Just fill up the test tube with aquarium water, add the drops from testing solution to your test tube, then match it to the color chart.  This method tests ammonia, pH, nitrite, nitrate carbonate, chlorine, alkalinity and water hardness and takes only a few minutes. The test tube and dropper test kit results are very accurate, is the least expensive cost per test and provides over 800 tests on average.

For more helpful information and expert tips on testing and maintaining the excellent water quality in your fish tank please see our article on How to Test the Water in an Aquarium.

Best Complete Test Kit for Freshwater Aquariums

Our top choice for best freshwater aquarium test kits is:

The API Freshwater Master Test Kit is on the top of our list. This easy to use and reasonably priced test kit is a well-established and trusted aquarium water test kit. With many years on the market, a long product shelf life and reliable results you can accurately test levels of ammonia, nitrates, nitrites and PH in your aquarium.

Affordable, easy to use and reliableOnly for freshwater aquariums
Delivers approximately 800 testsNot as precise as a scientific test meter
Includes the 5 most necessary water tests 

Best Complete Test Kit for Saltwater Aquariums

Testing your saltwater aquarium water with test tubes and droppers is simple. Just fill up the test tube with aquarium water, add the drops from testing solution to your test tube, then match it to the color chart.  This method tests ammonia, pH, nitrite, nitrate carbonate, chlorine, alkalinity and water hardness and takes only a few minutes. The test tube and dropper test kit results are very accurate, is the least expensive cost per test and provides over 800 tests on average.

For more helpful information and expert tips on establishing and maintaining the salinity in your saltwater aquarium please see our article on How to Maintain Salinity in a Saltwater Aquarium.

Our top choice for best saltwater aquarium test kits is:

The API Saltwater Master Test Kit is on the top of our list. This test kit is ideal for new and experienced saltwater aquarium owners. It comes with 4 glass tubes, 6 test bottles for testing pH, Ammonia, nitrate and nitrite levels which are essential test parameters supporting the nitrogen cycle. The easy-to-read color card provides an accurate comparison chart to identify your current tank conditions. The chart provides an excellent guide for correcting out of balance chemicals and maintaining a healthy environment for your fish, coral and live plants.

The API Saltwater Master Test Kit does not provide any additional testing capabilities for live corals and algae in the aquarium such as calcium, phosphate, magnesium, alkalinity and salinity. Before buying any test-kit be sure to check the expiration date printed on the product bottles and box.

Affordable and reliableTest kit is limited to ammonia, pH, nitrate and nitrite testing.
Easy to read comparison color chart 
Highest precision results (more than any other product comparison in the same category) 

Saltwater Aquarium parameters should be:

Alkalinity- 8-12 dKH

Calcium- 350-450 ppm

Magnesium- 1250-1350 ppm

Phosphate- <0.2ppm

Temperature- 75 – 80°F (23.5 – 26.5°C)

Salinity- 35ppt or 1.0264 specific gravity

Best Salinity Test Device for Saltwater Aquariums

The Salinity refractometer 0~100 PPT is one of the best salinity refractometers on the market today. With automatic temperature compensation and its chromium sensor housing this refractometer offers two scales of measurement, Specific Gravity (D 20/20) and parts per thousand. It is reasonably priced and very durable. If you have a saltwater tank this tool is a must have to accurately maintain ideal salinity.

Incredibly accurateMust regularly calibrate to maintain accuracy
Automatic temperature compensation 
Very durable 

Best Digital Scientific Meter and Probe

Some at home test kits, especially those which involve counting drops or comparing watercolor to chart colors can be difficult for some. The difference between the chart color above and the color below your water test color results can look very similar. If you look at the chart below you can see there is little difference between the safe ammonia levels of 0 ppm and the more deadly 0.25 ppm colors. The nitrite 1.0 ppm color is almost indistinguishable from 2.0 ppm color, and I don’t think it would be a stretch to confuse the toxic 5.0 ppm color as well.

As you become more involved in reef keeping you can invest in probes which can monitor parameter like PH and Salinity with the digital precision that only a scientific meter and probe can provide. There are advantages to investing in a digital water quality scientific meter testing system, such as:

  • Clear results easily seen on a digital display
  • Highly accurate results

There are several highly sophisticated and very expensive automated aquarium water testing systems on the market that will cost you $1,300 out of the box to as much as $8,000 for some custom home aquarium systems.

The downside with these “all-in-one” systems is that any equipment failure to your system may lead to you sending the equipment back to the manufacturer for repair. That means a single problem with one of your test parameters can lead to you losing all off your test equipment while it is being repaired. In our opinion the best option is to divide and conquer by using separate digital testers.

In our years of testing digital test equipment for aquariums we have concluded that Hanna Instruments provides the best digital meters on the market for aquarium water testing. The Hanna Instruments Marine Line of digital scientific meters and probes provide the best solution we know of. Hanna instruments have been a world leader in electro-analytical equipment since 1978 and they have a long-standing and well-earned reputation for making reliable, quality products that provide precision test results at an affordable price.

The digital test equipment we recommend provide you an instant readout for Nitrate, Nitrite, Phosphates, Calcium, Alkalinity, Ammonia, pH and salinity testing.

Our top choices for the Best Digital Scientific Meters and Probes are:

Digital Marine Nitrate High Range Testing (model H1782)

This is the best meter for freshwater or saltwater tanks with higher-than-average nutrient levels. Ideal for freshwater tanks with live plants or saltwater aquariums that are fish-only or have corals that can tolerate elevated levels of nitrate at 30 ppm or more.

Digital Marine Nitrate Low Range Testing (model H1781)

This is the best meter for use with saltwater tanks with delicate corals and invertebrates. The sensitive test parameter test very low levels of nitrates from 0.00 to 5.00 ppm.

Digital Nitrite High Range Colorimeter Testing (model H1708)

This is the best meter to provide you with more precise high range nitrite testing than the typical chemical test. This sensitive test parameter will test ranges of 0 to 150 ppm. This is ideal for standard testing of freshwater aquariums, or a low stress saltwater aquarium set up.

Digital Nitrite Low Range Testing (model H1707)

This is the best handheld digital low range nitrite test system. The highly sensitive testing parameter evaluates a range of 0 to 600 ppb. This is the optimum test parameter for saltwater aquariums with sensitive fish, invertebrates and corals.

Digital Phosphates High Range Colorimeter Testing (model H1717)

This Hanna handheld tester provides a cost effective and accurate way to measure phosphate. Phosphate is commonly found in aquarium plant food, but high levels may be counterproductive to your living aquarium. This colorimeter test ranges from 0.0 to 30.0 ppm.

Digital Phosphates Low Range Testing (model H1713)

This Hanna handheld tester provides a cost effective and accurate way to measure low levels of phosphate in your aquarium. Phosphate is commonly found in municipal water systems, aquarium plant fertilizers but high levels may be counterproductive to your living aquarium. This colorimeter test ranges from 0.0 to 2.50 ppm.

Digital Calcium Testing (model H1758)

This Hanna handheld tester provides a cost effective and accurate way to measure levels of calcium in your aquarium. Required for the development of calcium carbonate skeletons of coral reefs, calcium is a crucial component of marine waters. Designed as a more accurate alternative to standard chemical test kits, the Hanna calcium tester provides quick, accurate results in a few easy steps. The test range of this meter is 200 to 600 ppm.

Digital Freshwater Alkalinity Testing (model H1775)

This Hanna handheld tester provides a cost effective and accurate way to measure alkalinity levels in your freshwater aquarium. This test meter provides a test range from 0 to 500 ppm CaCO3. If you want to convert it to PPM to degrees of hardness, multiply the result by .056.

Digital Saltwater Alkalinity Testing (model H1772)

This Hanna handheld tester provides a cost effective and accurate way to measure alkalinity levels in your saltwater aquarium. The Hanna alkalinity colorimeter closes the distance between alkalinity test kits and advanced instrumentation.

Standard test kits are limited with accuracy since they depend upon the human eye to discern colors. The Hanna handheld colorimeter eliminates the struggle of matching to a color chart by providing a direct saltwater alkalinity result in ppm CaCO3. The testing range of this marine meter is 0 to 300 ppm CaCO3 and utilizes a highly accurate silicon photocell.

Digital Ammonia Low Range Testing (model H1700)

Present in water as a component of the nitrogen cycle, ammonia is excreted from animals and other organisms such as heterotrophic bacteria, actinomycetes, and fungi during the metabolism of proteins and amino acids. Generally present in small quantities in unpolluted waters, higher levels indicate organic pollution, and is toxic to aquatic life. The testing range of this highly sensitive marine meter is 0.00 to 3.00 ppm NH3-N.

Digital Ammonia Medium Range Testing (model H1715)

An excellent option for freshwater and saltwater tanks, the Hanna handheld ammonia colorimeter uses a highly sensitive silicon photocell to precisely determine ammonia and reagent coloration. The range sensitivity of this meter is from 0.00 to 9.99 ppm HN3-N.

Hanna Digital pH Checker Plus (model H198100)

The simple Hanna pH tester design is highly accurate to within 0.2 pH. The efficient design of the meter provides up to 1000 hours of continuous use from its Li-ion battery.  Hanna Instruments has a no-hassle replacement guarantee that they are well known for. There are other competitive digital pH meters on the market but Hanna provides excellent quality, design and customer care which makes their pH tester our top pick.

Digital Salinity Testing (model H198319)

The Hanna salinity tester is ideal for freshwater and saltwater applications. The simple design provides results in seconds in PPT (Parts Per Thousand), PSU (Practical Salinity Units) or S.G. (Specific Gravity). Many sensors on the market use stainless steel which oxidize over time and lose testing accuracy. The Hanna salinity tester uses graphite sensors which significantly reduces electromagnetic polarization and electrode decay.

You can expect up to 100 hours of continuous battery operation with a low battery blinking notification when it is time to change the battery. It comes with a protective case and is made with a durable casing for many years of reliable service.

Why do you Test the Water in your Aquarium?

Let’s talk about what you are testing and why these tests are important. We will break up the testing parameters across freshwater aquariums, live planted aquariums and saltwater aquariums below.

Parameters to Test in a Freshwater Aquarium


Testing your aquarium water for Nitrite is necessary to understand how well bacteria is breaking down ammonia. Bacteria converts the highly toxic ammonia to the less toxic Nitrite. While it is less toxic than ammonia, over time, high levels of nitrite will disrupt the metabolism of your fish and eventually destroy their oxygen carrying cells, resulting in the suffocation and death of your inhabitants.


Testing your aquarium water for nitrate will help you understand often you need to perform water changes. Nitrate is the least toxic of the 3 forms in the nitrogen and will be present in your water as beneficial bacteria convert nitrite to nitrate. At low levels these are not toxic to your fish, but at elevated levels this will cause stress to your fish and make them susceptible to disease. Nitrates can be reduced with regular water changes.


Testing your aquarium water for pH provides you with the baseline water chemistry of your tank to compare with what is found in the ideal conditions of the natural habitat. In freshwater, different fish species will have different pH needs so you will need to do your research to know what pH level is ideal for the inhabitants you keep. The lower the pH of the aquarium water, the more acidic it is and the higher the pH the more alkaline it is. In general, pH for freshwater tanks ranges from 6-8. Ammonia is more toxic to fish at higher pH levels and the production of nitrifying bacteria slows down when pH goes below 6.

General Water Hardness

Testing your aquarium water for water hardness is the measurement of calcium and magnesium ions. Some fish thrive in hard water, like cichlids while other fish like discus prefer soft water. You will need to do your research to know your ideal hardness level for the specific fish you keep in your aquarium.

Carbonate Hardness (KH)

Testing your aquarium water for carbonate hardness is the measurement of carbonates and bicarbonates dissolved in your water. You will need to do your research to know the ideal hardness level for the specific fish you keep in your aquarium.


Ammonia is the result of waste breaking down from fish and decaying plant matter. There are two types of ammonia in an aquarium.

  • Total ammonium (NH4) is the ionized version of ammonia and although it is toxic it is not as toxic as free ammonia.
  • Free ammonia (NH3) is the most toxic and dangerous form of ammonia to your aquarium.

Most water test kits will test for total ammonia, which make the results of testing less reliable. Testing your aquarium water for free ammonia provides the most relevant test results to determine toxicity levels.

Parameters to Test in a Freshwater Planted Tank

If you have live plants, you should also test for phosphate and iron levels.


Phosphate is a mineral based substance that supports photosynthesis. Testing your aquarium water for phosphate is vital to maintaining healthy biological functions in fish and healthy plant growth and development in freshwater tanks.


Testing your aquarium water for iron is necessary to prevent toxic levels from remaining in your aquarium water and building up in the fish internal organs which can lead to death. In planted tanks iron is a common micronutrient trace element needed for plants to produce chlorophyl (the green color in plants that help it to absorb light, create energy and grow).

Parameters to Test in a Saltwater Aquarium

The main parameters in a saltwater tank are mostly the same in Ammonia, Nitrite, Nitrite, Phosphate, and pH. The additional parameter to test in your aquarium water is salinity.


Salinity is best measured with a refractometer. For a saltwater tank with fish only, you can run your aquarium at 1.020, but coral reef tanks will generally run at 1.025 – 1.026 or 35 PPM.

Parameters to Test in a Saltwater Reef Aquarium

When you move into a saltwater reef tank, there are more water parameters to test in order to ensure your corals thrive. Below are the main parameters to test.


As mentioned in our Best Reef Salt Mix post, alkalinity is the fuel to build coral skeletons. Calcium and alkalinity relate to each which is way two-part solution is a common way of supplementing alkalinity.


Testing your aquarium water for Calcium is essential to know if your corals have the necessary building blocks to develop their skeletons and coralline algae. Without calcium, your corals will not build their skeleton and cannot maintain them.


Magnesium is a major element in reef tanks necessary for chemical and biological processes across all marine live in an aquarium. Testing your aquarium water for magnesium is essential for balancing alkalinity and catalyzing photosynthesis in plant life by supporting chlorophyll. Without magnesium plants, algae and coral would not be able to survive.

Trace Elements

Minor trace elements like Silica, Iodine, Strontium, Boron, Iron, and minor trace elements are typically tested through ICP water testing, which is something to consider if you are planning to run an advanced reef tank filled with Acropora corals. Trace elements do not contribute to the salinity of seawater and are used as supplemental nutrient sources enabling necessary biological and biochemical processes.

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