For those of us who keep SPS corals, maintaining a steady alkalinity has emerged as the key to success in keeping and growing corals. There are a wide variety of methods that you can use to maintain alkalinity that we won’t explore in detail right now. What we will deal with here is why alk swings occur in our tanks, how to prevent them, and how to recover from them while minimizing your coral losses.
Why is steady alkalinity so important to corals?
The most appropriate definition of alkalinity for reefkeeping revolves around the idea of how much acid (H+) is required to move a solution’s pH to a specific level. The specific level we are talking about is referred to as total alkalinity. Without getting too deep into the complex chemistry, this level is the point at which all carbonate and bicarbonate in a system is converted to carbonic acid. It is this total alkalinity that our test kits and hanna checkers give us a reading on, and what we strive to keep at a stable level in our tanks. Spikes in alkalinity commonly lead to burnt tips, loss of color, and necrosis in SPS corals, especially those in a low nutrient system. All of these things can be very damaging to the health and livelihood of corals, which is why we put such an emphasis on maintaining steady alkalinity.
What is an alk swing?
For our purposes, let’s refer to an alk swing as an event where the alkalinity (measured in dkH, Meq, or ppm) drops or rises by a significant amount within a short period of time. On average, it is suggested that the total alkalinity level be kept between 7-11dkh, the sweet spot for coral growth often varies for each tank. Based on our observations over the years, we have seen significant damage when alkalinity has risen or lowered by 1dkH or more within about an hour or less. This drastic change in alkalinity in such a short period of time can be deadly for corals.
How does an alk swing happen?
Now we know that we don’t want any changes in alk and we know the approximate minimum amount of change that is needed to affect our coral’s health. So, what are the ways in which these events happen in our reef aquariums? The truth is, there are many ways in which inexperience or equipment malfunction can trigger these events. Here, we’ve compiled a brief list of the most common causes of alk swings, based on our experiences with our systems over the past 20 years.
Over the years, equipment malfunction has been the leading cause of alkalinity swings in our tanks. In fact, what sparked us to write this article in the first place was two recent alk swings that were caused by our Apex controllers failing to do their job. The first time it happened our Apex, which controls our dosing pumps, randomly reset all of our switches to random on/off parameters. This caused our dosing pumps to remain on for a period of 4 hours straight. Our alkalinity went from 165ppm to 204ppm within an hour or so, and this sudden change killed over 400 SPS frags in one of our systems. The second alk swing occurred on the new Apex system we had just instilled. This time, we discovered the plastic hole for the reset button was not large enough which caused anything you plugged into the apex control module to depress the reset button. In our case, this factory reset on the apex amusingly turned “ON” all our dosing switches, and caused our alk to again rise from 146ppm to 181ppm in less than an hour. This completely wiped out another couple hundred frags a few weeks after the alk swing occurred.
These are only two examples of how technology can fail us, but there many more cases where technology is at fault for causing an alk swing.
Yes, it is possible we can make mistakes when dosing our systems. Whether we miscalculate the amount of buffer we should be dosing, or just use the very scientific “eye ball” method of dosing, human error can be responsible for a number of alk swings. Many years ago, we were using a Kalkwasser paste to kill many aiptasia in one of our systems when an alk swing was set off. Forgetting just how powerful the buffering and pH ability of the Kalkwasser was, we increased both of those parameters in our system. The increase took place in a matter of minutes which resulted in weeks of STN. This mistake on our behalf could have led to the death of more corals, thankfully in this case the corals recovered and re-encrusted.
Although there are many ways to spike alkalinity in a tank, there are also a variety of methods for recovering and preventing alk swings so that your corals stay happy and healthy. Stable alkalinity is absolutely crucial to keeping a tank with SPS corals and when maintained properly can lead to ideal coral growth. Stay tuned for Part 2, where we will dive into how alk swings affect corals and what you can do to manage and prevent them.