RSS The Water Change Conundrum

MASA Admin

8 May 2007
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We all have a friend in the hobby or know someone who constantly brags about how he or she has never done a water change and their tank is perfect. The corals are growing and colorful, the fish vibrant and active and all seems right in this tank. To add insult to injury, he also says that he rarely does any testing in the tank.  I have seen the comments and threads by numerous hobbyists making these claims and to be honest I am jealous. In all the years that I have been keeping reef tanks my tanks have never been successful when I wasn’t doing regular water changes on my tanks.

My 300 gallon tank a year ago

As we all know there are countless ways to set up successful tanks so I am neither advocating nor denigrating using one system or methodology or another.  I am an advocate of making things as simple and easy to do as possible. As I have learned through experience the easier something is to do the more likely I am to do it.  And I am assuming that most of my reef keeping brethren are the same. I think a continued discussion of this topic is especially warranted now since the Triton methodology for keeping a successful tank is gaining momentum.

Ben’s tank after doing a year of frequent water changes

The other reason I am bringing up this topic now is that approximately a year ago my friend Ben “Diesel” VanderNoort began a discussion of water changes on several sites and needless to say the varied opinions on the matter stirred much debate. As a result of going back and reading those threads it is clear that there are numerous opinions as to what is the “best” way to do this. Obviously there are the “no water change group” but this is still a minority. Then there are few who advocate the do a change when conditions are starting to deteriorate. But the majority two groups are the large change once a month group and the small frequent water change group. All of these groups have their advocates and their detractors.

Ben’s tank after doing a year of frequent water changes

Interestingly there is also a major difference of opinion as to why a water change is needed in the first place.  The largest group in these discussions advocates doing water changes as a means for adding substances that are used up by the tank’s inhabitants over time. The other group uses water changes as a means from removing undesirable compounds that have accumulated in a tank.

Close up of the colonies grown from frags in the same 1200

That many hobbyists are now worried about elements being used up and that a water change is a way to replenish things is markedly different than how water changes were viewed in the past. It is probably a testament to how good protein skimming and the use of resins and other compounds have become for removing everything from our tank’s water. I have always been more in favor of overskimming a tank and then adding in what I wanted rather than relying on a skimmer to remove the “right” stuff. But since I do now run very efficient skimmer I can see the value of this argument.

Used 50 gallon pickle barrel perfect for water changes

     For as long as I can remember, I had been doing large once a month water changes on my tanks.  On my old 1200 gallon tank I did a 300 gallon water change every month for 5 years and the tank did fine.  I did this size water change as I had a 300 gallon reservoir and when I set up the tank I set this up at the same time as I did the tank with all the related pumps and valves so that when a water change ws done it would result in the corals being out of for the water for as little time as possible. So when I downsized to a 300 gallon tank I moved down to a 50 gallon reservoir and did the same once a month water change pretty much for the same reason.  However, after the online discussion through Ben’s threads I decided to try something different.  For the next year I would do weekly 25 gallon water changes.

     Since I do weekly water testing, before I did the switch I kept a log of the tank’s parameters and here is the average for what they were for the 3 months prior to making the switch: 

  Nothing outstanding and nothing out of the ordinary.  So for this experiment I did not change anything else other than the water change rate and frequency.  I switched the GFO every 4 months just as I had in the past. The calcium reactor was run the same, and any other additives were all kept the same. Also for the 2 months prior to making the switch I weighed how much detritus, dry weight, was being removed during a water change. It was approximately 150 grams dry weight per water change.

     As with skimming I primarily do water changes to remove “bad” substances rather than to replenish what is missing so I was curious if doing more frequent changes would produce any results that could be quantified. So the average readings for the last 3 months of doing these 25 gallon weekly water changes were as follows:

Again nothing remarkable, just possibly an incremental improvement in the parameters, but nothing that demonstrated a marked change from when I did monthly changes.  Also note that the saltwater mix I used throughout was Instant Ocean, as has been the case since I began keeping reefs, so again nothing was changed that was being done to the tank except more frequent water changes. One thing that was noted that by doing more frequent water changes, more detritus was being removed as the dry weight of detritus during the last two months of water changes average between 80-100 grams dry weight. So almost a pound of detritus was being remove per month while the previous change system removed less than half this amount.

Tank today, showing the health and colors in the corals

Since I view the tank daily it was hard for me to see overall significant differences, but my videographer Russ Kikel usually only sees the tank once a quarter when we are making videos so he was much more attuned to letting me know if there was any difference. For the first 6 months neither he nor I really saw much of a difference. The tank has always been packed with corals and fish and despite the heavy bioload has done well.  However at about the 6 month mark I noticed that many corals that had not really shown much growth suddenly started to really take off. Similarly when he came over the first thing he noted that while he couldn’t put his finger on it, the overall colors of the corals really seemed to be much brighter. When we compared video that he had been taken the year before with video of the present, it was clear that there was significant growth and the coloration of the corals had indeed become more intense.

Tank today, showing the health and colors in the corals

      I have included pictures from both a year ago and the present for comparison. I will acknowledge that I do move corals around and in and out of my tanks so obviously only those corals that can be seen in each picture can be compared, and this may be difficult as I wish I were a better photographer. So for anyone close by you are welcome to stop and see for yourself.  Also my tank contains more fish and corals than most tanks, so their effects of more frequent water changes could be more impressive in my tank owing to how much quicker bad substances probably accumulate.  But for everyone who has seen the tank a year apart, the comments have been very consistent. The colors of the blue, green and purple corals now really pop in comparison to how they looked a year ago. And while I do accept that this improvement in color may simply be the result of their finally acclimating to the tank and then growing, some of these corals had been in the tank for over two years before I started doing more frequent water changes and had shown little to no growth over this time.

Tank today, showing the health and colors in the corals

      As has been discussed countless times there are countless ways to successfully set up and manage a reef tank and everyone has an idea of what is best for them.  I know this is a single example, but for me, and possibly Ben, who has seen similar results, doing more frequent small water changes may incrementally improve the success of the tank.  Since for the most part we are now as successful as we have ever been in keeping the myriad organisms that we now do, most of our improvements will be incremental and doing small water changes may be one of them.  Maybe next in one of my tanks I will try the Triton method of no water changes. After all like most of us I strive for making the hobby as easy and as much fun as possible.

Tank today, showing the health and colors in the corals

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