Aquarium Test Kit: When & How to Accurately Check Your Tank

Aquarium test kits are one of the most important tools for successful aquarium keeping. Water testing opens a window to the invisible world of aquarium water quality.

Unfortunately, some aquarists don’t take water testing seriously until something goes wrong in the tank. Water quality rarely declines at a fast pace. Periodic testing gives you a “heads up” on what’s happening in the aquarium before conditions drift to potentially harmful levels.

best rated test kits for saltwater and freshwater aquariums

But aquarium testing is more than just preventing disaster. Test kits allow us to fine tune the aquatic environment, so our fish, plants and invertebrates look great. You can even get a handle on algae-promoting nutrients, so your aquarium will stay cleaner with less maintenance!

We’ll discuss what you should be testing for based on the type of aquarium. Then, we’ll take a close look at test kit technology and which is best for you.

Basic Water Quality Test Parameters

  • pH: The measure of acidity of the water.
  • GH: General hardness is the measure of calcium and magnesium (water hardness).
  • KH: Carbonate hardness is the measure of carbonates (alkalinity), which stabilize the pH.
  • NH3/NH4: Ammonia is a harmful waste product released by fish and invertebrates. Ammonia is converted to nitrite by the biological filter.
  • NO2-: Nitrite is harmful but is converted to relatively harmless nitrate by the biological filter.
  • NO3-: Nitrate is the end product of biological filtration. It can be used by algae and plants as a nutrient.
  • PO43-: Phosphate is a nutrient used by algae and plants.

Freshwater Fish and Planted Aquariums

As far as water parameters are concerned, the term “freshwater aquarium” covers a wide range of conditions.

A freshwater tank containing discus will typically have low water hardness and an acidic pH with low alkalinity. An African cichlid aquarium will have a high pH and very high water hardness and alkalinity. A community aquarium will be somewhere in the middle.

The good news is that most community freshwater fish thrive in a wide range of water conditions, making it easy to keep many types of tropical fish.

Ammonia and nitrite should always be zero, no matter what kind of aquarium you’re keeping.

Nitrate is considered an indicator of overall water quality. When nitrate levels increase due to feeding and fish waste, it’s time to make a water change.

The phosphate level is an especially valuable test when keeping live plants. Plants and algae like light and need the same nutrients to live. But the idea is to have just enough nutrients to keep the plants growing but not enough to stimulate algae growth.

Carbon dioxide (CO2) supplies carbon for aquatic plants. Many aquarists who use CO2 injection monitor the level of carbon dioxide to maximize plant growth.

Below is a list of water quality parameters and ranges recommended for the most popular types of freshwater aquariums.

Community Aquarium

  • pH: 6.8 – 7.5
  • GH: 7-10 dGH
  • KH: 8-20 dKH
  • NH3/NH4: 0 ppm
  • NO2-: 0 ppm
  • NO3-: 20-40 ppm
  • PO43-: < 20 ppm

African Cichlids

  • pH: 7.6 – 8.2
  • GH: 7-10 dGH
  • KH: 10-15 dKH
  • NH3/NH4: 0 ppm
  • NO2-: 0 ppm
  • NO3-: 20-40 ppm
  • PO43-: < 20 ppm

Amazonian Biotope Aquarium

  • pH: 5.5 – 6.5
  • GH: 1-3 dGH
  • KH: 1-3 dKH
  • NH3/NH4: 0 ppm
  • NO2-: 0 ppm
  • NO3-: 20-30 ppm
  • PO43-: < 20 ppm

Planted Aquariums

  • pH: 5.5 – 7.5
  • GH: 3-8 dGH
  • KH: 3-8 dKH
  • NH3/NH4: 0 ppm
  • NO2-: 0 ppm
  • NO3-: 20-30 ppm
  • PO43-: < 0.5 ppm
  • CO2: 15-30 ppm

Saltwater and Reef Aquariums

Saltwater aquariums are classified into the fish-only and reef aquarium categories.

If you’re keeping a fish or fish only with live rock (FOWLR) tank, testing is relatively simple. You’ll want to monitor ammonia and nitrite, always making sure the levels are zero.

Since pH and carbonate hardness (alkalinity) go hand-in-hand, both should be monitored. Saltwater fish don’t appear to be super-sensitive to nitrate but it is a good idea to test anyway. Nitrate is an indicator of biological breakdown of fish waste and food, so if the level climbs it means a water change may be necessary.

Reef aquariums with live corals require more advanced testing to monitor the trace elements required by reef-building SPS and LPS corals.

In addition to the normal saltwater tests, reef aquarists keep track of phosphate. Phosphate build-up can stimulate algae growth. The formation of calcium carbonate by corals is somewhat inhibited by phosphate.

Silicate is one of the most common minerals in groundwater. It is used by marine diatom algae to form their skeletons. Diatoms form a brownish coating in live rock and aquarium glass. Silicate tends to slip through reverse osmosis systems and can cause unsightly brown patches in the aquarium.

A silicate test kit allows you to test your tap water, aquarium and reverse osmosis water for silicate break-through.

Calcium (Ca) and magnesium (Mg) levels must be maintained for the corals to grow and thrive. Calcium and magnesium test kits make it easy to monitor levels and use additives that boost these important elements.

Optional tests include strontium and iodine, two important trace elements used by encrusting coralline algae, SPS and LPS corals and other invertebrates.

Saltwater fish and FOWLR aquariums

  • pH: 8.1 – 8.4
  • NH3/NH4: 0 ppm
  • NO2-: 0 ppm
  • NO3-: 20-30 ppm
  • PO43-: < 20 ppm
  • Alkalinity: 8-12 dKH

Additional tests and parameters for Reef aquariums

  • NO3-: < 20ppm
  • Calcium: 350-450 ppm
  • Magnesium: 1250-1350 ppm
  • Phosphate: < 0.2 ppm
  • Silicate: <0.5 ppm
  • Iodine: 0.03 - 0.06 ppm
  • Strontium: 7-9 ppm

How do aquarium test kits work?

Aquarium test kits are based on established analytical test methods used by laboratories for water testing. The tests are often simplified for home aquarium users.

All the kits are colorimetric, meaning the end result of the test procedure forms a color. The color corresponds to the level of the substance being tested.

For example, when there is no detectable ammonia in the water, the result will be yellow. As the ammonia level increases, the test result will shift to shades of green.

Some tests are titrations, meaning a chemical is added to the test tube, drop by drop, until a certain color either appears or disappears (called the end point), indicating the test is complete.

The number of drops required to reach the end point is used to calculate the level. The test chemicals can be in liquid or powder form.

Dip strips have the test chemicals already applied to the strip. Just dip and read the color.

Colorimetic tests rely on your ability to accurately see the color in the test tube or dip strip and match it to a color card. It’s a quick and inexpensive test method used in laboratories, aquaculture facilities and water treatment plants.

Even though there is variability caused by each person’s ability to perceive color and correctly match the test to a color chart, these tests have proven to be accurate and very helpful, especially to aquarists.

The next level in water testing takes the “human factor” out of interpreting the test result. In analytical laboratories, very expensive optical devices “read” the color in the test tube, then averaging the result. It’s a super-accurate method but too expensive for the home aquarist.

But thanks to technology, small hand-held “colorimeters” have become available to aquarists. Each colorimeter is designed to test a single parameter, like calcium or phosphate.

The advantage of having a colorimeter is that the device can detect very fine variations of color. It is much more sensitive and accurate than “eyeballing” the color and matching it to a color card.

This type of test costs more than a traditional aquarium test kit and requires a separate colorimeter for each parameter.

Which test kit style is right for you?

If you’re a basic freshwater aquarium hobbyist with a simple aquarium set-up, dip strip testing is for you. Dip strips are easy, convenient and require no handling of chemicals.

There are no liquid drops to add to a test tube. You don’t have to measure out scoops of powder. Just dip the test strip into the water and compare the results to the color card. Some dip strip tests have several parameters on one strip, making it easy to give your aquarium’s water quality a quick check-up.

Liquid test kits are a little more complex. You’ll have to take a water sample and carefully add liquid or dry chemicals to the test vial. The tests require shaking the test tube for a specific time frame then allowing the color to develop before matching with the color chart.

Some test kits, like water hardness and alkalinity (KH), use the titration method. You’ll add one drop of test chemical at a time, until the water sample changes color. These kits require more time and care to use.

Many aquarists like the increased accuracy and test range of liquid test kits. If you're more of a specialty freshwater aquarist with a planted tank, cichlids or breeding sensitive fish, liquid test kits are recommended.

The same goes for saltwater and reef enthusiasts. Marine life like corals are especially sensitive to improper water chemistry. Specialty saltwater and reef test kits are designed to test saltwater and provide highly accurate results. Some of the test parameters important to reef aquarium care, like calcium and magnesium, are only available in a liquid test kit format.​

The electronic colorimeter-style tests are highly accurate and eliminate the interferences caused by ambient lighting and bias of the human eye.

For most aquarists this level of sophistication is not necessary. But for reef aquarists and coral fraggers, these test kits make it much easier to zero in on very specific levels of calcium, alkalinity and other parameters critical to raising corals. These test kits are the closest thing to a home laboratory most aquarists can afford.​

Speaking of laboratories, you can send your reef’s water to a lab for analysis.

ICP (Inductively Coupled Plasma optical emission spectrometry) is the best method of testing for trace metals in water. Reef aquarists are very interested in monitoring levels of essential trace elements like strontium, iodine and other trace elements as well as harmful metals like aluminum and lead.

ICP testing services, set-up specifically for saltwater testing, will analyze your aquarium water and provide an analysis of every metal found in the sea. ICP provides reef aquarists keeping LPS and SPS corals with information that used to only be available to laboratories and universities.

Tips for proper use of aquarium test kits

No matter what type of test kit your select, the accuracy of the results depend mainly on following proper testing techniques.

Here’s our list of tips that will eliminate many of the testing errors aquarists run into when testing at home.

  • Read all of the testing instructions. Each step must be followed for the kit to work properly. Become familiar with the steps before testing.
  • Don’t rush. Rushing always leads to missed steps, adding the wrong amount of test chemical or forgetting something important.
  • Add the chemicals exactly like the instructions state, in the order described.
  • Shake the test chemical bottle or vial for exactly the specified time. This is especially important when testing nitrate.
  • Allow the test color to develop as instructed. No more, no less.
  • Compare the test results to the color card in natural daylight conditions. Bluish reef lighting and yellowish incandescent lighting can make it difficult to match colors.
  • Rinse out the test vials with freshwater after completing the test. Never let the vials sit with old water and chemicals. It can stain the glass and leave residue in the test tubes.

How often should the aquarium be tested?

Frequency of testing depends on the condition and type of aquarium you’re keeping.

Newly set-up tanks that are going through the initial break-in period, should be tested at least once a week for ammonia and nitrite until levels drop to zero. Other parameters can be tested frequently until the stability and natural trends of the aquarium are known.

Some aquarists with a stable pH can test once every few weeks.

An acidic aquarium with very low alkalinity and pH should be tested every week since the pH buffering is relatively unstable.

The best advice is to experiment and learn how often each parameter needs to me monitored. Remember, you’re looking to spot slight shifts in parameters to prevent larger swings.

If your tank almost always checks out OK, that’s a good thing! It’s like getting a good report form the doctor. Who could be disappointed with good news?

Proper care of aquarium test kits

Be especially careful to store dip strips in a dry location with the cap tightly sealed. Never put wet fingers into the strip jar!

Keep all test kits away from very warm or freezing temperatures. Lab tests show that aquarium test kits are stable, even when briefly exposed to extreme temperatures, but should not continuously be stored in adverse conditions.

All test kits have a limited lifespan. The expiration clock begins ticking as soon as the test kit is manufactured. Some test kits have a long shelf life of several years. Others have only one or two years before they expire. Look for Use-By dating on the package. Don’t use aquarium test kits after they’ve expired.

Aquarium Test kit Reviews

1. API Test Kits

API is one of the founding companies in the aquarium trade. The company has been around for over 30 years.

API test kits are the best-selling test kits in the aquarium hobby and are used at universities and aquaculture centers world-wide.

All API test kits come with glass test tubes and plastic snap caps. Instructional booklets provide detailed instructions on how to perform each test and what the results mean.

API sells individual test kits and master test kits for saltwater, reef and freshwater aquariums. The pH, ammonia, nitrite and nitrate test kits are industry standards for their accuracy and ease of use. Each test solution bottle includes expiration dating.

API also makes specialty tests for phosphate, high range pH for African cichlids and saltwater tanks, Calcium for reef enthusiast along with alkalinity (KH) and general hardness (GH).

The Freshwater, Saltwater and Reef Master test kits combine popular tests for one easy to use kit.

If you’re a fan of dip strips, API offers 5-in-1 testing strips (Nitrite, nitrate, pH, GH and KH) and a separate ammonia dip strip. Ammonia testing cannot be combined with other tests on a single strip. Dip strips are a favorite among freshwater aquarists looking for fast and easy water testing.

2. Salifert

Salifert test kits are aimed at reef-keepers. The Holland-based company offers the usual water test kits for ammonia, nitrite, nitrate and pH.

But they also have phosphate, alkalinity, magnesium and calcium kits, which are especially important for keeping SPS and LPS corals.

And there’s more! Salifert makes a silicate test kit for testing aquariums, tap water, deionized water and RO water.

Silicate is an essential element for diatom algae. If the water has silicate it could stimulate nuisance algae blooms.

You’ll also be able to test for strontium and iodine too! Perfect for maintaining live corals.

The company is now offering multiple kits in specialty packs. Salifert kits come with clear instructions and color charts. Test tubes are made of clear plastic and include caps.

3. Red Sea

RedSea test kits come as individual test kits and in combo packs.

Calcium, magnesium and alkalinity tests are available separately along with phosphate, nitrate and iodine.

Combo packs include Reef Foundation Pro (calcium, magnesium and alkalinity), Trace Colors Pro (iodine, potassium and iron), and Algae Control Pro (phosphate and nitrate).

Red Sea kits use measuring devices that make taking water samples and dispensing into the test vials fast and accurate. Instructions are easy to understand with simple instructions.

Test chemical refills are also available. This saves money because you don’t have to buy the vials, instructions and dispensers again.

All of the test results can be compared to the Red Sea Reef Care Program. The program ties test results to the Red Sea reef supplements for easy dosing and monitoring of water quality parameters.

4. Hanna Instruments

This Italian company has been designing innovative water testing instruments for over 40 years. The company’s roots are in laboratory and industrial process control.

Hanna took their innovations and know-how and created high-tech water testing technology in an aquarist-friendly package.

Colorimeters used to be reserved for laboratories with a big budget. Hanna changed that by introducing their Checker colorimeters.

The Checker eliminates user error when reading and matching colors to a chart. The colorimeter senses the color and calculates the results for you.

You’ll need an individual Checker for each parameter you want to test.

Many of the Checker kits are geared toward reef aquarists looking for accurate low-range measurements of phosphate, nitrate, nitrate and ammonia, but they work equally well in freshwater too.

If you don’t need to this level of detection for these parameters, Hanna offers Checkers for calcium, magnesium and alkalinity and iodine. The Hanna kits include test chemicals and a pipette for performing the tests.

Maybe you’re just looking for a reliable pH meter that doesn’t cost a fortune. Hanna’s got that too! The Pocket pH tester is waterproof with an LCD display. More importantly, the pH meter is easily calibrated using Hanna calibration solutions. pH meters need periodic calibration to remain accurate. The Pocket pH Meter makes it easy to get accurate pH levels in fresh or saltwater.

5. Seachem

Seachem is a US-based company run by a chemist. It should be no surprise that Seachem test kits are some of the most complex testing kits in the hobby. The test kits will remind you of a chemistry class!

Each kit comes with tiny measuring scoops and titrators for adding test chemicals into the test vials. Some tests even require filtering out particles from the test solution.

Seachem testing instructions are lengthy, with many steps required to obtain a result. Some kits can be performed in a low or high-range scale, allowing you to zoom in on trace levels.

The kits use tiny bottles of chemicals that you measure out with little scoops or squeeze to dispense drops.

Be prepared to spend considerable time performing each test.

You’ll find Seachem test kits for fresh and saltwater aquariums, but the focus of the company seems to be on the reef hobby. The list of tests includes:

  • Ammonia
  • Nitrite/Nitrate
  • pH and Alkalinity
  • Iron
  • Phosphate
  • Silicate
  • Copper

While Seachem is known for making complex test kits, they’ve also created a simple ammonia test that continuously monitors your aquarium’s ammonia level.

The Ammonia Alert test sits inside the aquarium sensing even trace amounts of ammonia. The sensor changes color if ammonia is present. Many aquarists use the Ammonia Alert in quarantine tanks as a quick way to keep watch on the water quality.

6. Nyos

NYOS is a German manufacturer best known for their protein skimmers and water pumps. The company also makes test kits and additives for reef aquariums.

The Nyos Reefer test kits are limited to five reef-specific parameters. These include alkalinity, nitrate, calcium, magnesium and phosphate.

Nyos test kits come with a German-made, precision calibrated dropper for precise and consistent testing.

The kits use only German-produced test chemicals manufactured under EN ISO 9001 standards.

NYOS Reefer test kits use two glass vials for color comparison. The first vial is a “blank,” containing only aquarium water. The test is performed in the second vial. Both vials are used to match the color card. The idea behind the blank vial is to compensate for yellow tint in the aquarium water.

Reefer test kits are simple to use with few steps to complete the tests. High-quality glass vials and precision droppers and dry chemical scoops make water testing straight forward and fast.

7. Triton Lab ICP Analysis

Triton Lab, located in Germany, offers a way to affordably measure 35 seawater elements using Inductively Coupled Plasma - Optical Emission Spectrometry, or “ICP” for short.

The test kit includes two vials for water samples. Just fill the vials with aquarium water, place them in the shipping envelope, and drop the envelope in the mail.

The water samples are sent to Germany for analysis. You’ll be able to view the results online in 10-14 days.

The Triton website has helpful tabs that explain what the results mean and how to correct or maintain each element or water parameter.

8. LaMotte

LaMotte has been manufacturing water test kits for the water treatment, laboratory and aquaculture fields for over 35 years.

LaMotte aquarium-style test kits use the same rugged components and plastic cases as their field kits.

The kits have a look and feel of an industrial-grade test kit. There’s no pretty reef graphics or fancy guide to keeping your fish or corals. You will find the kits to be easy to use with straightforward instructions.

Many of the test kits use a sturdy color comparator that holds a translucent color strip and the testing tube, making it easier to match the color results.

You’ll find that LaMotte offers the main water parameters most aquarists are looking for: pH, phosphate, ammonia, nitrite, nitrate, water hardness, alkalinity, iron and oxygen.

9. ATI

ATI provides saltwater testing using ICP (Inductively Coupled Plasma - Optical Emission Spectrometry).

The kit includes three vials for taking aquarium water samples, which are sent to the lab for testing.

The ATI analysis provides a comprehensive chemical analysis of 43 parameters, providing the complete picture of your reef’s water quality. You’ll be able to view the results online.

Subsequent ICP tests are logged onto your personal account so you can track trends over time.

ATI also makes a variety of reef supplements designed to work with the ICP analysis.

The online report will make recommendations for correcting deficiencies by using their ATI trace element treatments.

Test Kit Recommendations

For overall value, accuracy and simplicity, API Master Test Kits remain at the top of the list. No matter what kind of aquarium you’re keeping, API has the main tests you’ll need.

Reef aquarists sometimes want to monitor nutrients, like phosphate and nitrate, at trace levels. To measure levels below .25 ppm, color comparison cards need to be specially printed with subtle shades that match the trace levels.

Nyos Reef test kits have color charts that dip down into this range.

Salifert test kits are also quick, easy and have color charts in the low range.

Hanna Checkers are really cool because they're a real piece of lab equipment designed for eliminating our vision and color-matching limitations. Plus, they’re good for freshwater and marine testing.

If you’re a reef aquarist and really want to know the state of the trace elements in your aquarium, there’s nothing better than an ICP analysis from ATI or Triton Lab.

If you have any questions or comments, feel free to post them below!