The Importance of Water Testing

"Well, we know where we're going, but we don't know where we've been," sang the Talking Heads in We're on the Road to Nowhere, and that is how a lot of hobbyists view testing their water. They know where the parameters should be, but they either don't know how to get them there or keep track of what they were to see how they have changed. Sadly, many of us, myself included, think we know our water's parameters and that they are good by merely looking at the tank and seeing how the corals are doing. I have been contacted many times by hobbyists asking why a coral died, or why all of their recently added new corals died while their old corals were doing great, or why they all of a sudden had an algae bloom, etc. When I ask what their water parameters are, they invariably reply either they were perfect or didn't know. Like the song, you can't see where the tank is headed unless you know where it's been.

Like equipment maintenance, water changes, quarantining animals, and cleaning the glass, water testing is an unglamorous task that is one of the most crucial aspects for having long-term success in the hobby. Regardless of how good your lights are, how efficient your skimmer is, or the flow rate, none of these matters if you don't have good consistent water quality at the proper levels. You can't tell just by looking at the tank how good your water quality is. When changes occur suddenly, you know it as your dead corals tell you quickly. But when the parameters degrade gradually over time, the corals either acclimate to these changes or gradually fail too.

Testing Variability

Testing the levels of all the essential parameters is probably one of the least fun aspects of keeping a tank and does require some time to do it right. And to be honest, most test kits only really give you a ballpark value for what your tank's parameters are. It has been documented there is variability in the measurements between test kits from different companies, between kits from the same company, and variability caused by user error. There can also be variability from when a kit is new to when it gets old; that is why the better kits now have an expiration date. It is recognized that reagents, especially liquid ones, can deteriorate over time and give inaccurate readings. Before I became obsessive about testing my water, some of my test kits were over three years old, and I realized that they were useless in many cases at that age. I even had an alkalinity test kit that was older than that. I knew it was old, but thought to myself, how could things deteriorate that much, and what difference would it make. Since I was biased to believe that my water was good and most of the corals looked okay, I assumed that the measurements were spot on and thought this until I started consistently losing corals one by one. Not seeing a problem with my test kit, I brought my tank's water to a shop to have them test it. Initially, all of the measurements came back good until they got to alkalinity. The alkalinity in my tank was off the charts at 17, the old alkalinity test kit I had been using was off by over 9 points, and not many corals can tolerate this high level for very long. This wake-up call kickstarted me to test the water more frequently. Now my Alkatronic unit tests alkalinity 6X per day, and because I am obsessive, I still test it manually once a week. Salinity, calcium, magnesium, potassium, pH nitrate, and phosphate are also tested weekly.

Salinity Testing

Of all of the parameters that we test for, salinity is the most important, yet it is tested the least and taken for granted. This parameter is the most important in keeping a saltwater tank. It is a measurement total for all the dissolved solids in a marine aquarium, and all other parameters are dependent on it being at the proper level. It should remain stable as measured as a salinity at 1.0264 (35ppt), which is normal seawater. There has been some conjecture that running it at higher or lower levels may have some benefit, but I have not seen this in experiments I have run. And as mentioned, when the level varies from this, the concentrations of alkalinity, calcium, magnesium, etc., will also fluctuate. So, it is best to keep a tank consistently at this level. It should be noted, the smaller the tank volume, the easier it is for salinity to fluctuate, which means a smaller tank should be tested more often.

Track Parameters

All of the values for the parameters obtained should be kept in a log either on paper or on an Excel spreadsheet. Putting them into a spreadsheet can take longer than doing the actual test, so I have found just keeping a paper log easier. But if you want to do them on a spreadsheet, this will allow you to graph the values over time. It is vital to use test kits with very clear coloration changes when the endpoint is reached and accurate when testing. I am a big fan of making things easy, as that way, I am more likely to do them. For these reasons, I use a wide variety of test kits, including Elos, Salifert, and Nyos kits, for most of my tests now, as I like when the color changes are robust. I have found these kits accurate and for the color change to be robust and not subtle.

Consistency is Key to Testing

Despite how little I like to do the testing, I have found several things that make it easier and the results more reliable. First, the more often I do a test, the quicker I can do it. For the tests I only do less frequently, like strontium and ammonia, I still read the testing directions every time, and this often doubles the time it takes to do the test. For the tests I usually do, I can do them without reading the directions as I know them by heart, so they get done faster. I also do the tests the same way every time I do them, precisely measuring the tank water, tilting the dropper bottles, and time of day. All of these variables can significantly change the test results.

My testing is done every Saturday at the same time, and the tests are even done in the same order. By testing this way, the conditions in the tank are approximately the same, so if something is out of whack, it is more likely to be detected since the tests are done consistently at the same time. I also do each of the tests twice. I know most of us only do a second test when the readings are off from what we expect, and sometimes we even do them until we get a reading we want. But due to user error, the tests are just as likely to be off and look correct as off and be incorrect. Also, to make sure I am not missing anything, each test is done twice, and the measurements are compared. As long as there is no difference greater than ten percent, I assume the tests are good, but if there is a significant difference between them, I run two more tests.

More than nine times out of ten, the readings are consistent, but now and then, they differ markedly. When this occurs, I run two more tests and then try to determine why the tests differed from each other. I have found that there are a lot of ways to introduce user error when doing testing. It can be as simple as using the top of the meniscus for the water level in one test and the bottom for the other or adding the drops differently or miscounting. So, now I try to be consistent in doing all of these things both within tests and between tests. Since I do them often, my consistency has improved markedly.

Test Make-Up Water Before Water Changes

I not only test the water in all of my tanks weekly, and I have five reef tanks, but I also test the water for water changes before it is added to any tank. I also test the water from any vendor I have received corals from before the coral is added to my tank. I do this so I know how much I need to gradually acclimate a new coral so that it does not become stressed.

The make-up water is tested to make sure it is consistent from batch to batch. At times in the past, I have seen my tank look worse after a water change when it should look the same or better, and when that happens, I needed to figure out why. Then I started testing it to determine if it was markedly different from my tank's water. For the most part, most freshly made-up synthetic saltwater is consistent from batch to batch, and mine is made up a week before it is used for a water change, and I use the same vendor I have for 35 years. And for the most part, it has been consistent over this entire period. However, my tap water has varied as I have lived in different spots and at other times of the year, depending on what the municipal authority adds to the water. So, for these reasons, each batch of make-up water is tested too. I use Instant Ocean for my make-up water mainly because I have been using it for all these years, and it is consistent from batch to batch. But I also know that it is consistently low in magnesium. Since I know this and I also know how much it is off by, I just add the proper amount of magnesium to each batch when I mix it up so that it is the same as that of my tank.

Test Water from New Corals

I test the water in the bags from newly acquired corals because with salt mixes, I have found that the water in my tanks can be significantly different from the salt in other tanks. In this way, if a coral I get does not do well, I have a starting point as to why. It also gives me an idea of how long and what I need to do to acclimate a new coral to my tank. If the water from another tank that a coral has come from is markedly different, it may take two or three days to acclimate it to the conditions in my tank.

By acclimating corals where the water it came from is significantly different from mine, doing a gradual acclimation dramatically increases the likelihood of its long-term survival. And considering what we are paying for frags and how much we hate to lose any coral, knowing the differences and acclimating accordingly is the least we can do to enhance the likelihood of a successful acquisition.

ICP Tests

In addition to doing regular testing of the major elements in my tank, I now regularly have the trace elements tested. ICP (Inductively Coupled Plasma) testing is a relatively new complex chemical method for testing the levels of minor trace elements that can be as low as in the parts per billion range. Up until approximately the last six years, there was no good way to measure the levels for many of the trace elements, so at best, we guessed what their levels were and added trace element mixes to replace them. Now with this technology readily available, these trace elements can be measured regularly and added accordingly. There are a wide variety of ICP tests currently available. I have used at least six of them as I run an ICP test quarterly if my tanks are good and monthly if there are problems. None of them are perfect, as their values are created using each company's own proprietary algorithm. Still, for the most part, they are all fairly consistent in their evaluations. I have found them extremely useful for tracking down problems such as heavy metal poisoning or providing baselines to allow for proper additions of trace elements.

Water testing is not rocket science, and performing it correctly does not require a degree in chemistry. But doing it regularly and keeping a log of your results will go a long way in helping you have long-term success in the hobby. As I learned in my tanks the hard way, you can't tell what's in the water without testing it. And while it will probably never be fun, it does provide a sense of pride when your tests match up and give you something to work with to keep your tank at its most beautiful state.