Stability and Consistency of a Reef Tank
One of the benefits I have found of writing so much is that when I am putting together an article I always learn something. When I did the articles on the master’s tanks I learned a great deal, as I hoped I would. One of the most important things I learned from these individuals is that all of them believe that stability is one of the keys to their success. Most of them not only keep the parameters of their tanks very stable, but they also are not constantly adding or changing the fish and corals in their tanks either. Something I really need to do a better job of doing. While it is clear that some of the parameters of their systems vary markedly from one another, there seems to be little variance in their systems over time. Seeing that these variances seemed to do little in terms of limiting their success made me question them on how stable their tanks were. This led to questions in terms of how stable are they daily, monthly and yearly. It also made me look at the consistency between their tanks. That is what parameters seemed to be consistent versus which ones showed a great deal of variance. While every accepts the notion that stability is one of the keys to long-term success, for the most part I have not been able to find scientific documentation as to what exactly are the limits to this “stability”.
Keeping a tank long-term tank like this one requires the conditions to be both consistent and stable.
In this successful tank of Dr Sanjay Joshi the corals are allowed to grow and are not constantly moved around. When he wants to add new corals he clears a space and then allows them to grow as seen by the cleared space on the left.
According to Wikipedia, the definition of chemical stability is the quality of being stable, resistant to change or deterioration. So while our goal may be to keep our tanks stable, the very nature of a reef tank is the opposite, in that there are constant forces at work that cause change and produce deterioration in the water quality and other parameters of our tanks. Consumption of calcium, carbonate and trace elements constantly change the parameters as do feeding and the resultant fish waste. This is also the case on an actual reef, but here the changes are generally not as great owing to the vast amount water and strong water movement that dilute and limit any rapid fluctuations from occurring. So what we try to do to mimic the reefs is control by various means and limit the effects these fluctuations have on our tanks. So instead of saying the goal is to keep our tanks stable it may be better to say we want our tanks to be consistent, which by definition means they are unchanging and steady. However, even when say this we can fall into a trap as the question then becomes what are we trying to have our tanks be consistent with? Natural seawater is the obvious answer, but even here there is a great deal of variability. When I visited Jamie Craggs at the Horniman Museum last Fall, one of the interesting things I saw, besides his spawning corals and their offspring, was a slip of paper hanging on his wall. On this paper were the parameters of the water from various areas of different reefs where Jamie had collected samples and then sent them of to Triton for ICP analysis. Looking at the paper made it clear that instead of the oceans around the reefs all having the same readings, as I expected, there was a great deal of variability amongst just about all of the various parameters. The water around these various reefs around the world where water had been collected wasn’t consistent at all. I also believe that I read that Dana Riddle, in some of his writing showed significant variability as well, even when he just took his readings from different reefs around Hawaii. However, rather than this being alarming it is actually somewhat comforting, as it indicates that there is a much wider range in which corals can grow and they are much more accepting of greater variability than I had suspected. This is good for us, as it means we don’t have to be perfect with the parameters in our tanks. But as experience has taught us, our corals are still not happy and will fail to thrive if their tank’s parameters fluctuate wildly in short time spans.
In the tank of Julian Sprung the stability of alkalinity and calcium are maintained by dosing that is done in 10 minute intervals.
From my own experience and from talking with others it is clear that while some fluctuation in a tank’s parameters are tolerable to the corals there are some limits in how much things can fluctuate and that there are some limits. Of the various parameters that tend to fluctuate daily the one I have found to be the most impactful is alkalinity. Due to various mishaps, laziness or poor measuring skills I have over the years developed a keen insight into just how important it is for the long-term success and health of my corals to keep the alkalinity in my tanks from changing too much or too rapidly. It is generally thought to be best to limit daily fluctuations in alkalinity to being less than 1 dKH and to keep it in the range of from approximately 8-10 dKH. In my 300-gallon and in my former 1200-gallon tank this has been the goal as well, but over time due to the density of sps corals and their growth at times the fluctuation in these tanks was significantly greater than this at times. As a result, when this occurred, STN starting at the base of the corals occurred. Also when other parameters were not optimal, even a fluctuation of .8-1.0 was enough to cause this problem to occur as well. Because of my understanding how difficult it is to stop STN once it starts I went to daily or twice daily manual testing of alkalinity in my tanks for the past year. Fortunately, during the past 2 months I was able to improve the stability and monitoring in my tank with the purchase of Dastaco Calcium reactors and a kH Guardian. Using these two devices the alkalinity and calcium levels of my tank now show less than .5 dKH variation throughout the day and night. As a result, in my opinion, the corals in my tank have shown faster growth than was the case when there was less stability. Similarly, in Sanjay Joshi’s tank, which is a tank I see almost monthly, the growth in his corals has also increased as he has minimized his alkalinity variability. Sanjay keeps his alkalinity on what some might consider the high side, as he does with his nutrient levels as well, and keeping all of these factors high also undoubtedly contributes to what I consider the unprecedented growth he sees in his tank. I should note from what I and others have seen not all corals tolerate fluctuations in alkalinity equally nor do some tolerate high or low levels. From my experience and talking with others chalices and the echinata types of Acropora like Hawkins do not tolerate high alkalinity of over 11. Similarly Pectinias and Symphyllias do not seem to like low pH resulting from low alkalinity. Both Sanjay and I have lost Pectinia colonies when we let these values drop too low. I will be writing an entire article on my experience and opinion on alkalinity in a later article, but for the purpose of this article it is my opinion that we should strive to maintain the consistency of the alkalinity levels in our tanks so that the fluctuation during the course of a day is as minimal as possible.
When alkalinity is allowed to fluctuate too widely STN can occur as it did here on this Acropora.
Pectinias like this one do not tolerate low pH or high alkalinity.
Going hand in hand with the fluctuation in alkalinity is the instability of pH. As with alkalinity, pH fluctuates as CO2 and oxygen are consumed and given off during the course of the day and night via respiration of the fish and corals in our tanks. As a result, the pH in our tanks is usually highest right before the lights go out and lowest right before they come on. The general consensus is that the pH in our tanks should range around 7.8-8.2 with it possibly ranging from 7.6-8.4 without any real problems being seen. In my own tank, the pH ranges from 7.9 in the morning to 8.2 at night and my tank is packed densely with fish and corals. I must admit that at times in the past the pH in my tank ran lower and the stability of the pH level was much lower as before I made some adjustments and additions it often dropped as low as 7.5 and some times barely reached 8.0 to 8.1 as a high. When the pH in my tank was running this low and was this unstable there was definitely less growth and poorer coloration in the corals. To try and stabilize the pH several adjustments were made. For the past 9 months or so nano bubbles are generated starting right before the lights go out in order to keep the oxygen level high in the tank at night. In addition, an oxygen reactor using ozone was added to further increase the oxygen level in the tank, but also to oxidize detritus in the water column that was settling out and deteriorating and thus also lowering the oxygen level and as a result lowering the pH of the tank at night. These were not expensive or elaborate additions to what was being done on the tank before, but for me at least they have helped stabilize and increase the pH of the tank, as well as improve the overall oxygen level I believe.
Soft coral tanks like this one of mine can tolerate wider fluctuations than do sps tanks.
Tanks like Stuart Bertram's are closely monitored so that fluctuations are kept to a minimum and new fish or corals are only rarely added.
The above two parameters are two of the biggest in terms of variability and how their instability can impact a tank, but there are at least a couple of others that can impact a tank as well. The first of these is temperature. Now that LEDs are the most common light being used, the impact that our lights, especially metal halides, have on the temperature and the temperature fluctuation in our tanks has been greatly reduced. But LEDs still produce some heat and now especially that it is summer, tanks can still run hot and there still can be significant fluctuation and inconsistency in the temperature a tank stays at during the day. Prior to my switching from halides to LEDs it was not uncommon for the temperature in my tank to vary as much as 5 degrees during the course of a day. For the most part this did not negatively affect the corals health or growth, as long as the other parameters were stable and optimal. But if something was amiss, then this instability added to the problem in the tank. For various reasons over the years, I have had my tanks drop to as low as 68 degrees and get as high as 85 degrees. In both instances, as long as the temperature was then adjusted back to normal slowly there was little damage to the corals. I only learned the value of slow temperature adjustment after making the mistake of rapidly lowering the temperature a couple of times and having significant losses as a result. Therefore, as with the other parameters, if things get out of whack it is better to bring them back in line slowly rather than making rapid adjustments. How tolerant are corals to temperature swings and high temperatures if they are done slowly. Well in the case of my friend Mark Silverman’s tank I learned than when done slowly the tolerance of some Acropora is remarkable. When his tank was set up two pumps were set up to return water from the sump. But the pumps were too strong, so only one could run at a time, so they were set up so that one would run and return water from one side of the tank for 5 hours and 45 minutes, shut down, and then the other would kick on and return water from the other side. For some reason, that I never fully understood, for 30 minutes twice a day neither pump would be on and the tank would drain down slightly. Initially this was not a problem, but over time as the corals grew eventually some of them would be exposed during this time. This more or less mimicked what happens on some reefs where the corals are exposed to the sun at low tide and are out of the water. What was interesting is that because these corals were exposed to this variability in temperature and water level slowly they not only tolerated it, but they thrived in this condition as the one Acropora valida that grew out of the water the most was one of the most brilliantly colored corals I have ever seen. And it may not seem like anything unique, but this coral was exposed to a 400-watt metal halide and all its related heat for 30 minutes each day. When we took the temperature at the coral when it was out of the water under the halide it was over 120 degrees. Despite this, because the situation was consistent, the coral grew to tolerate it. This showed not only how tolerant corals can be but also how even when conditions are not what we consider optimal if they are consistent and stable corals will thrive.
When you keep lots of fish and a mixed tank as I do, it is often difficult to maintain consistency of the tank's parameters, so frequent testing is required.
Even when conditions seem perfect problems can arise. Only when you test over a 24 hour period can you see how much conditions vary and how unstable your tank may be.
As with temperature, a lot ha changed and improved with the use of LEDs, especially in terms of stability. In the past, over time halides would deteriorate and their amount and type of light they produced would not only change in intensity, but would also change in color temperature. So when old halides were switched out for new, there could be a dramatic change in how how much and what color light was hitting our corals. As a result, the light duration had to be reduced as did the intensity so lights were raised or some shielding was placed under the new lights lest they burn all the corals. Fortunately, this is not the case with LEDs, but there still can be inconsistency when new corals are acquired and placed under these lights. For people new to LEDs, one of the first thing that appears to them is that these lights do not seem as bright as do halides. This is because unlike halides, which despite often being housed in good reflectors, light form LEDs is focused down and not throughout the room. So when we first see them the light they are producing seems significantly less than what we were used to. Because of this, and I did this, when I first put an LED light over my tank I ran it full blast right from the get go because it did not appear very bright. This was a very costly lesson, as in reality it is at least as bright, but more focused and this focused intense light had an amazing capacity to burn corals since they were not allowed to acclimate to it slowly. As shown in the above example, when corals are allowed to adjust slowly to change and the change is consistent, they can adjust. Fortunately, with LEDs it is not necessary to replace them so once they are added the light they produce is consistent and stable and over time they can be brought up to full power. I take 3 months to get my lights to this level to prevent even the slightest chance of burning from occurring. However, this begs the question, then what do I do when I add new corals? The answer is simple: you need to acclimate them slowly to the new light to reduce the likelihood of burning them. In my own tanks, I place them in a mesh basket and give them 6-8 weeks to gradually be acclimated to the light they will eventually be exposed to. So they start at the bottom of the tank and are gradually moved up to their desired location. This may seem like a lot of work, but when frags cost what they do now there really is little alternative.
While beautiful tanks like this one of Julian Heccavaria and Cruz Arias are more common now than ever, they still require consistency and frequent testing.
Compared to the early years of the hobby, when stability and consistency were relatively little understood concepts in the hobby, they now are one hallmarks of most successful tanks. After talking with and seeing a lot of tanks over the past year I have endeavored to make my tanks more stable and am trying to reduce the amount of tinkering and adding and moving fish and corals that have been one of the enjoyable yet also frustrating aspects of my reefkeeping. Seeing so many tanks where the fish and corals were once placed, were allowed to simply thrive and grow made me appreciate once again how beautiful even a “unnamed” coral can be as a big healthy colony that can be seen from across the room. Working to make our tanks be more stable and the parameters more consistent, rather than in a seeming constant state of flux I think will go a long way toward bringing myself and I think other reefers even more enjoyment in the hobby. While having perfectly stable conditions in a tank is not a prerequisite for success, I think it greatly increases the likelihood of it occurring.