Mail-In and ICP Aquarium Water Testing: Which Service is Right for You?

Reef aquarists have always been concerned with water quality.

At first, testing was limited to basic water parameters like nitrate, phosphate and calcium. More advanced test kits were developed for trace elements such as strontium and iodine. But we’ve always wished we could test for “everything”, especially all the trace elements.

Colorimetric (color-matching) and titration (drop by drop) test methods don’t exist for the majority of trace elements found in sea water. Most marine salts claim to contain every element found in the sea. But how do we know if they’re really in the salt mix? And if they are, how long do they last in our reef tanks?

Up until now, we had no way of knowing the levels of the majority of the elements in our water. This type of water analysis was available only to those who had access to a university or advanced water testing laboratory. And even then, the lab had to have their testing equipment calibrated for seawater analysis.

But all that has changed thanks to forward-thinking companies who recognized the need for advanced water testing geared toward reef keeping. It’s now possible to obtain an analysis of your aquarium water showing every element and its level in relation to natural sea water.

ICP-OES Testing

Those six letters stand for inductively coupled plasma optical emission spectrometry. That’s a mouthful, but here’s what you need to know.

ICP-OES analysis is one of the most powerful tools for the determination of trace elements. A sample of aquarium water is injected into the machine. The water is nebulized into an aerosol and sent into an argon plasma furnace. The individual elements in the vapor are atomized and ionized. The elements are then detected and quantified by the optical emission spectrometer (OES), which measures the intensity of radiation emitted at the element-specific wavelength. This measurement is converted to individual seawater elemental concentrations in the mg/l and ug/l range. The ICP-OES machine must be calibrated to seawater elemental standards in order to compare the seawater sample to know trace element levels stored in the machines calibration software.

If all this is too much information, here’s the simple explanation.

Take a water sample from your tank, send it to the lab and they’ll tell you what elements are in the water and how they compare to natural seawater.

Mail-In Water Testing Options

There are many ICP and water testing labs but they are not prepared to accept and test saltwater samples from our aquariums. Only labs with specially-calibrated equipment can analyze the water samples from our aquariums.

Currently there are four major water testing labs specializing in saltwater analysis: (CoralVue), Aqua Medic AWT, Triton Labs, and ATI Lab. The process begins by purchasing an analysis kit.

All kits include:

  • Vials for water samples
  • Instructions on taking the water samples and sending them to the lab
  • Instructions about registering online to track the results
  • A return shipper to send the water samples to the lab

ICP-Analysis (CoralVue) and AWT (Aqua Medic) water samples are shipped to Colorado for analysis here in the USA. The other labs, based in Germany, require water samples to be collected at the US staging location and forwarded in bulk to the labs in Germany. Each testing service offers a slightly different array of elements in their analysis report.

Matrix of Elements Tested By 4 Mail-In Water Testing Services

Mail-In and ICP Aquarium Water Testing: Which Service is Right for You?It’s important to know the difference between elements and compounds. ICP-OES is capable of testing elements like calcium, sodium, phosphorous and iodine. Substances like nitrate, nitrite, phosphate, carbonate hardness and ammonia are compounds and can’t be measured by ICP-OES. Other analytical methods, like ion chromatography, are used to measure these substances in the aquarium water sample. Some labs don’t bother to test ammonia and nitrite. The reason being these parameters can be tested at home. There is also concern that ammonia and nitrite are unstable and may be acted upon by bacteria during shipment to the lab, causing the test results to be unreliable.

Testing the Testing Labs

We wanted to see what it was like to go through the “ICP Experience” with each of these four testing services. A single batch of saltwater was mixed using Tropic Marine Pro Reef salt mix and RO/DI water. The water was mixed for an hour to ensure complete dissolution of the salts. Identical water samples were taken and sent to all four testing labs. The goal is to look at variances within the results, which are expected, but more importantly compare the benefits of each service in order to help you make the best decision for your reef tank.

ATI LabATI Lab - From $39.95

The ATI analysis covers 43 parameters. The kit comes with three vials for aquarium water and one for optional RO/DI testing. Each vial has a barcode that will link the water samples to your on-line account. By registering at the ATI website you’ll be able to create a profile for one or more aquariums, track the water sample linked to the aquarium, view the results and add additional tests to each aquarium’s profile.


The ATI kit comes with a pre-paid return label and shipping bag. Water samples are collected in the US and shipped to the lab in Germany twice a week. Results are usually available in about two weeks. ATI calculates salinity based on the sodium and chloride level. From there, the analysis software determines the proper concentration of each element based the salinity level. The baseline (reference value) is natural seawater (NSW) at a particular salinity. ATI explains the details on their website, but the idea is to maintain the right ratio of elements at the salinity your keep your tank at. ATI ranks the water’s “balance” from 0 to a score of 100%. Since the baseline is NSW, elevated calcium, magnesium, strontium and other elements is considered an imbalance and lowers the score. There’s also a breakdown of all the elements in chart form. You see what the level is in your aquarium vs ideal NSW levels. It’s important to interpret the results with this factor in mind. Your water may score low because you’re adding calcium for the corals. The analysis report makes recommendations for correcting imbalances through water changes and ATI products.

Triton LabTriton Lab - From $49

Triton ICP analysis covers 36 parameters. The kit comes with two aquarium water sample vials and barcode stickers. You apply the stickers to the vials. The code is used to register the water sample to your account. The kit box is used as the return shipper, so be careful when opening it up. You’ll have to bring the return shipper to the post office to purchase return postage. Water samples are forwarded to Germany for analysis. The analysis report is broken down into elemental categories that include trace elements, heavy metals, major elements and nutrients.

Triton Triton

The online report uses a “warning lamp” sliding color scale. Green is good, yellow is a warning and red means there is a critical imbalance. You’ll be able to compare your water’s analysis to NSW standards. Triton says that the entire process from shipping to receiving analysis can take 10-14 days. Triton has helpful calculators on their website that help you manage the elemental balance of your aquarium water. The website provides dosing calculators for Triton reef supplement products. (CoralVue) - $29.95

The CoralVue ICP analysis covers 33 parameters (Update: now 40+). The kit comes with one vial for the aquarium water sample, an identification label and return shipping envelope. Register your aquarium online for a unique water sample code. You have to write your information on the label and apply the label to the vial. The return shipper comes with an address label but you’ll have to provide the postage. The lab promises a 48-hour turnaround once the sample reaches the Lakewood, Colorado laboratory. The online report is interactive. You can see multiple aquariums if they are registered. The report resembles a periodic chart. (CoralVue) (CoralVue)

Clicking on an element allows you to individually compare the level to four different oceanic regions. You can choose from Fiji, Hawaii, St. Thomas and Florida. Results can also be downloaded as a simple pdf report. The online results page does not make recommendations on dosing supplements or correcting imbalances in the water. There is a link to “Water Additives” but no content is available on the page.

Aqua Medic Aquarium Water TestingAWT (Aqua Medic) - From $46.99

The AWT from Aqua Medic covers 13 parameters and technically does not utilize an ICP machine to perform the water tests.  Instead they use a combination of lab grade colorimeters, spectrometers and auto-titration methods. The word "ICP" has become synonymous with these mail-in water testing services and will often be used to refer to the AWT service but in fact, no ICP testing machines are used. You will notice AWT tests for compounds that none of the other services offer such as nitrate and alkalinity which are certainly among the most useful parameters to watch closely. AWT is also the oldest water testing service for aquariums in the USA.

AWT Water Testing Service (Aqua Medic USA) AWT Water Testing Service (Aqua Medic USA)

The AWT kit comes with two water sample vials and information about sending the water sample to the US lab. The return shipper is a USPS Priority Mail box with pre-paid shipping. You don’t have to actually register to receive the test results. The lab will email the basic results within 48 hours after receiving the water sample. If you set up a registration on the website, you can graph ICP test results by date. The idea is watch and see if there are any trends in elemental deficiencies or build-up over time. The online report lists the parameter, a verbal rating of high, low and good and the level (mg/l) of each parameter. The report also offers a brief paragraph about each parameter and explains what the NSW level is, along with recommendations for adjusting the level to bring the tank into balance. Iron and boron are optional tests that require an additional fee for the analysis.

Comparison of the Results

The following chart compares the results of all four testing labs.

Mail-In and ICP Aquarium Water Testing: Which Service is Right for You?

Final Thoughts

Each testing company has developed a product they believe best serves their customer’s needs.

AWT tests for only the main elements that reef aquarists can adjust with supplements, water changes and filtration media and feeding practices. ATI Lab, and Triton Lab test for many more elements.

It has been suggested that many of the trace elements, if present at all, are in the salt mix as unavoidable contaminants and that testing is unnecessary. Other reef aquarists want to know the levels of “everything” out of curiosity. ICP-OES equipment must be calibrated for every element you want to test for. Reducing the number of elements in the analysis cuts costs related to chemicals and calibration time.

The good news is there’s a choice. All of the testing labs make it easy to take water samples, send them in and then track the results on-line. You can dive deep into elemental analysis of your water or just take a look at the elements you can control with everyday reef practices.

ICP test comparison chart

What does this mean for you?

Look first at what you want to know and then how quick you need to know it. Are you constantly thinking about Arsenic getting into your tank and killing off your pets?  Probably not, but you might always be questioning whether or not your alkalinity test kit is giving you accurate results. In this case, the AWT would be a great choice because it provides you an overview of the most important parameters for keeping a healthy reef tank and will quickly give you the information you need in order to make changes before they become detrimental to the animals inside your tank.

You may be an SPS guru with a mature aquarium and really want to boost the colors or growth rates among your prized collection of corals. In this case, you likely have your head wrapped around keeping the major elements in check and assuring waste is not a problem in the tank. Something like ATI Lab would be a great benefit to you because you can finally see how all of the elements change over time in your tank and with your water changes, if you're doing any!  You can then change or alter the levels or your methods to reach your desired water chemistry.

Every tank is different, what happens in your tank may not be the case in my tank.  The only way to be sure is test your water and devise your own plan for success based on this knowledge that is now easily accessible for any hobbyist.