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Aquarium Test Kits – Which One to Use?

Test Kits

When I hear hobbyists talk about test kits, the conversation reminds me of some of the conversations I have heard about beer. “Oh that beer is good, but not as good as this beer.” or “I can’t believe anybody would drink that cheap beer.” Except instead of talking about beers, they are talking about aquarium test kits.

More than a few times, I’ve had a customer tell me that their fish store sold them a test kit when they got their aquarium, but they didn’t really know what to do with it.

Some of them went online and saw the same conversations I read, and then realized that the aquarium test kit they had was the one the hobbyists were comparing to the cheap beer… so they weren’t sure what to think after that.


Different aquarium test kits have different strengths

I have performed thousands of water tests with several lines of aquarium test kits. I make it a point to switch brands every now and then and to test them side-by-side to compare the results.

While working with them, I have found that most aquarium test kits are generally accurate and user-friendly. But there are a couple of variables which, depending on your preferences, can influence which one is best for you and your aquarium.


Aquarium Test Kits and Human Error

Even the most careful person is likely to miss by a drop or two every now and then. They might draw a quarter ounce too much of aquarium water, or squeeze a bottle harder and get bigger drops of the reagent, skip a drop while counting, etc…

Depending on the aquarium test kit, one drop can mean a big difference. One drop in API’s KH test equals 1 dKH. Many aquarists agree that there is a big difference between 8 dKH and 9 dKH. That same drop in Salifert’s KH test kit can be around .05 dKH, depending on the size of the drop.


Accuracy of Aquarium Test Kits

My experience has shown me that different aquarium test kits have different degrees of accuracy  (see How Close is “Close Enough?”). For example, API tests give a general idea of water quality levels, and SeaChem tests are known for pinpoint accuracy.

Bad batches of test kits exist, and there can be variations within a batch of aquarium test kit reagents. Some companies include control samples inside their kit so that you can test the sample to make sure that the kit is measuring accurately.


Ease of Use

Some aquarium test kits are easier to use than others. Some are simply counting drops or matching colors. Others are more complex processes or take more time to complete.

Red Sea’s Nitrate Pro test kit is an example of both. It involves using two vials of water, both from the aquarium and RO filtered, three bottles of reagent, a color wheel to match the results, and an apparatus to hold all of the parts together. The test takes 9-minutes to get the result, and if it measures near the end of the high range or the low range, then you need to test again to dial in an accurate measurement. This can be a 20-minute test.

Compare that to API’s 6 minutes or Salifert’s 3 minutes.


Ease of Reading the Results

This is usually more of an issue with color-match tests as opposed to titration tests (where you add a reagent drop by drop until the water sample changes color and see how much you used, which gives you the result).

I have seen more than a few occasions in which one test sample would show three different results in three differently lit rooms.

Some tests have such a slight difference between levels that it is very difficult to get a reading. API’s test for copper is a great example of this, as is Salifert’s pH test.


It Comes Down to Needs and Personal Preference

When I am asked about what aquarium test kit to use, the first question I ask is How Close is “Close Enough”? Do you need pinpoint accuracy, or a general idea of where things are? After that, it depends on their personal preferences, like how easy it is to do the test, the methods used, and other factors.


Things to Consider, Brand by Brand

In my experience working with aquarium test kits over the years, I have noticed some general tendencies among differed brands.


Aquarium Pharmaceuticals (API)

API aquarium test kits are generally simple to use. Hobbyists tend to downplay their accuracy, but they have compared pretty consistently with the other test kits I have used. They are not known for pinpoint measurements, but they are useful for checking general levels in water quality.

Some of their color matches can be hard to read, but for the purposes of testing a saltwater aquarium, if levels are that high, then the high level is more concerning to me than the actual resulting number.

Nitrates, for example, are easy to read at regular to mid-high levels. Once you get over 40ppm, though (higher than most aquarium owners want their nitrates to be), it’s hard to pinpoint the level.

The Ammonia and Nitrite tests are effective when it comes to answering “is it in the aquarium?”. But not as effective when answering “how much is in there?”. I can get a general idea, but with these two toxins, how much isn’t usually as important to me as their presence.

In general, I’ve seen their tests do a good job at establishing general levels, although I was surprised at how accurate the calcium test could be (even if it could be a bit messy).


Red Sea

Working with Red Sea’s aquarium test kits leaves me with mixed thoughts. They are usually accurate. If I am measuring Iodine, Potassium, or Iron, I am most likely using their test. Their support on the internet is pretty thorough, too.

The Ammonia, Nitrite, pH and KH tests were simple to use, and the layout of their color matching made it easier to get an accurate reading. But the other tests had enough issues that I try not to use them.

For example, 9 minutes to get the result for a Nitrate test (6 for the Phosphate Pro test) is a long time to wait (and if you need to retest into the other range, you have 20 minutes invested into it).

The color matches are close enough to each other to make some of the tests difficult to read, and I have experienced problems with their bottles. Either they wouldn’t dispense consistently, clog easily, or even leak (Phosphate Pro B has been the most guilty bottle of leaking for me).



Overall, the Salifert aquarium test kits are efficient. With a little practice, after you get good at titration, accurate results get measured quickly. You can measure KH and Calcium levels accurately in less than a minute. Their Nitrate test is a 3-minute dwell time, and Phosphates is close to instant.

Their Ammonia and Nitrite tests indicated their presence in the water every time I used them. Sometimes, when I was facing one direction in the right light, I would get a zero reading, but when I faced another direction, the kit would test positive.



SeaChem tests are historically spot-on accurate. When I ask “How close is ‘close enough’?”, I am quoting one of their scientists when she was telling me about the company’s philosophies.

SeaChem’s copper test is the only one that I have confidence in when I need a copper reading. A slightly wrong reading on copper can have a strong adverse effect on an aquarium (even with their accuracy, the color match can be tricky, and I often ask a second person to look at the result for verification).

Their tests can be complex. Aquarium owners who don’t need the pinpoint accuracy that SeaChem provides should consider other aquarium test kits. But if you just need a general idea of what’s happening in you tank, some of the other test kits are more practical choices.


Test Strips

Test strips are a quick way to get a very basic level. They are not known for their accuracy. But the right test strips can be somewhat useful in the right circumstances.

When a new tank is cycling and you need to see if there is any Ammonia left over, test strips can be handy in detecting whether or not it’s in there. How much is not as important as the fact that ammonia is in there at all.

They can also be useful when someone has an aquarium which has stabilized long enough that the levels are always consistent. Test strips can give a basic visual of a tank’s parameters. I one of the colors is off, then it indicates that something has changed, and then you can investigate it further.

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