Chronic Stress in Captive Tangs

Juvenile chevron tang (Ctenochaetus hawaiiensis)

Juvenile chevron tang (Ctenochaetus hawaiiensis)

Tangs and surgeonfish are a diverse, beautiful, and often highly personable group of fish. It is no wonder that so many of us want to keep these fish in our systems. Inexperienced keepers do the right thing by going to their favorite forums and sites to ask which tangs can be kept, what size tank is appropriate, and how many they can keep in a particular system.

Unfortunately, there has long been disagreement among certain hobbyists on precisely how to answer these questions—with some being much more restrictive than others when it comes to the species, tank sizes, and number of specimens recommended. In some instances, heated arguments occur as a result. Folks on both sides of the issue are generally well-meaning. Certainly neither side wants to bring harm to captive tangs. So why all the fuss then?

An overlooked ailment

I believe a good deal of the original disagreement actually stemmed from problems created by an unrelated group of ailments that few people at the time correctly identified. While I can’t be much help in resolving any lingering disputes, maybe the following information can be of help to some of my new-to-tang-keeping friends out there.

For several years, my high school students and I have been passively involved in stress hormone studies of parrotfish with University of Toledo Medical Center professor Dr. John Turner. He successfully linked empirical data showing that increased stress causes numerous health conditions observed in parrotfish on coral reefs around the Caribbean Sea and the Bahamas island chain. The same sort of research has not been conducted on tangs, so I am making a suppositional leap from parrots to tangs, but I firmly believe the two groups of species respond in similar ways to increased hormone production induced by stress.

The effects of chronic stress

What does stress have to do with housing tangs in captivity? Everything. Any tang will live in a small tank, at least for a time. But as each day passes, the odds of the fish’s demise increase. Why? Chronic stress! Fish rarely die of stress. Rather, they succumb to the effects stress has on their bodies.

Increased stress experienced over a long period causes numerous negative effects. Dr. Turner found that in areas where the parrotfish experienced regular elevated levels of stress (in other words chronic stress) parrots were fewer in number, lower in reproduction rates, smaller in size, and far more likely to exhibit symptoms of various disorders and diseases. In short, chronic stress is killing off whole populations of parrotfish.

Each species of tang and surgeonfish has its own niche in the world. Yet each group shares the same basic needs: enough room to roam, a variety of foods, and places to avoid the aggression of others. Some keepers observed that tangs kept in smaller tanks seemed more likely to develop diseases or other health conditions or simply fail to thrive. But because they didn’t identify stress as the root cause, their advice to house tangs in larger tanks was not always well received.

Their critics were not completely off base, as no empirical data exists clearly demonstrating an ideal minimum aquarium size for any species of tang. What is generally clear, however, is that the bigger the tank, the better the tang’s chances of surviving.

How big is big enough?

Yellow tang (Zebrasoma flavescens)

Yellow tang (Zebrasoma flavescens)

Recommended tank size is the most common area of disagreement in the tang-keeping debate. After countless requests for specific advice, experienced keepers came up with some arbitrary minimum sizes—typically in the range of 125 to 150 gallons. But then other keepers will claim their tangs are doing great in a 90-gallon or even smaller tank.

However, what we don’t often hear about is long-term success keeping tangs in those small tanks. Far too often we hear tang deaths being attributed to ich, a spike in dissolved nutrients, a fight with a tankmate, a “weird disease,” “just plain bad luck,” or some other unknown cause.

I am asserting that the root cause of most of the above deaths is actually chronic stress. The keeper failed to provide proper space for the species to swim comfortably, enough safe hiding places in order to avoid the occasional aggression that happens even in the most peaceful of tanks, or a balanced diet of the right greens and high-quality meaty foods.

I know what you are thinking: “I don’t have a big tank, so that must mean no tangs for me.” That is not exactly what I am saying. I am saying that you need to meet the requirements of your particular tang. There are a couple of tang species that will do fine even in a tank as small as 90 gallons. For example, both Kole tangs (Ctenochaetus strigosus) and chevrons (Ctenochaetus hawaiiensis) are relatively small as adults and usually adapt to a limited amount of swimming room far better than the tangs that grow to a foot in length or more.

While it is quite possible to keep those species, I am not saying that every 90-gallon system is necessarily right for them either. The keeper must build their system with the tang’s needs in mind. The tang should be the biggest fish in the system. The system must also be free of smaller but harassing fish, such as sixline wrasses (Pseudocheilinus hexataenia), or very territorial fish like some clown species. Rockwork must be arranged to allow the tang to seek shelter whenever it feels the need and to have a safe place to sleep at night. Equally important, the keeper must provide a regularly available source of grazing greens and a daily variety of meaty foods.

Of course, having a large system does not automatically mean you can keep a tang or group of different tang species. Again, long-term success hinges on the keeper meeting that species’ or group of species’ special needs. It is important to remember that the best chance of success in keeping a group of tangs in the same tank is to add the least aggressive fish first and then slowly add the rougher ones later (and smaller if possible). Again, providing hiding places, proper nutrition, and tolerable tankmates are critical in creating a low-stress environment.

Tough questions, elusive answers

There are two more questions related to chronic stress and tangs. The first is, which species are compatible with each other in your aquarium? The second is whether it’s okay to buy a juvenile tang with the intention of either buying a bigger system later or simply passing the fish on to someone with a bigger tank later.

These questions aren’t any easier to answer than our first questions. Species compatibility is tough because fish don’t all respond to the same stimulus in the same way. Two identical tanks stocked with identical species groupings often vary in the level of aggression and other interactions. The bottom line here is that each individual is a risk in terms of how well it will get along and how well it will adapt to a captive environment. Keepers reduce their risk by looking at general trends. If you are reading from multiple sources that a certain two or three tang species are often successfully kept together, the risk of failure will be less than if you are reading the opposite.

As for the second question, I discourage keepers from buying young fish with the intention of trading up to a larger tank or trading the fish away when they get too big for their system. Far too often, fish in these scenarios don’t live long enough to be moved to a larger home. Even the small versions of our favorite fish experience a great deal of stress just as their adult counterparts would and for the exact same reasons.

We can prevent chronic stress!

Chronic stress, brought on by us failing to meet all of a tang’s needs, compromises the fish’s ability to fight off diseases and to thrive in general. Keeping a fish for a few weeks or months is not long enough to claim success. The effects of chronic stress may take months to even a year or more to become fully evident. This fact is not an excuse for poor husbandry.

If you ask me whether you are safe in keeping a certain tang in a specific system, my answer will not be based upon arbitrary tank sizes, but rather on how the entire environment comes together for the tang. After all, I am acting in your best interest as well as my own. Buying a fish that will not live a year in your system is not only a waste of the fish’s life and your money, but it also drives the price up for the next person, as the demand is one fish higher than it should be.


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About David Bowers

David Bowers is the marine biology teacher at Bellevue City Schools in Ohio. David is also an adjunct instructor of coral reef ecology at the University of Toledo and has worked as a marine science education consultant for the University of Houston. He has over 20 years of saltwater aquarium keeping experience.


  1. This is a great article for the general care of Tangs. The family of Tangs are reef roamers grazing on algae covered rock, hence algae is critical in their diet for long term health. While they graze on algae turf they inadvertently consume tiny crustaceans living in the algae, hence the need to feed them some meaty foods such as Mysis shrimp, clam or small pieces of silversides.

    Quarantining them for 30 days minimum, in an appropriate QT set up, is crucial to their adjustment to your feeding schedule and will go a long way in insuring them an easy transition into your display tank (DT). Tangs are hyper fish with a high metabolism and need room to roam. On the reef they constantly swim covering vast areas in a days time. Our aquariums, even the largest, are nothing more than closet space compared to their natural home, and hardly the right quarters to house them in. Yet, given the right conditions, Tangs not only survive but thrive in captivity.

    Thank you David Bowers for sharing your expertise on one of my favorite families of fish.

    Dick Hilgers

  2. Paul Baldassano says

    I have a theory about tangs and other schooling fish. Tangs almost always live in schools, some small schools and some numbering in the thousands. Such a fish was “designed” to live in a school like a boat was designed to “live” in the water. A tang has a very well developed lateral line that allows it to swim in a school, fin’s length’s away from the next fish. It allows it to “feel” the movements of the fish next to it and instantly adjust it’s heading. If you have ever dove with tangs, they all turn in unison. They also can dive into a coral head without even knowing if they can fit, but they always manage to get in. I think that in a situation like a square sided glass tank, the fish constantly gets echo’s from the glass which confuses it. I also feel that is the reason for the high rates of HLLE in these types of fish. Some sharks also have a problem in tanks for almost the same reason as they have a well developed “sonar” system mostly in their head. They keep getting echo’s from the walls even though there is nothing there as they can’t see the glass from where they are just as we can’t see the glass we are looking through. My other part of this theory is that tangs were designed with a deep body just so their lateral line could be made longer as it curves up and over their back. Just a theory of course, but I like it.

    • David Bowers says

      Paul and Richard, I would like to thank you both for taking time to share your thoughts about tangs. I am not sure how I would be able to quantify a tang’s need for space due to its habit of swimming in open water when its not grazing. Of course I suspect the need is related to staying healthy. However, I hesitate to say it is true with no direct evidence to support the notion. Regarding the feeding of micro creatures; you are right on the money. Poor diet and too little space to move freely coupled with issues of interactions with other fish and inverts and there is a formula for potential failure.

  3. What’s the difference between a small tank size with one tang and a large tank with many different types of tangs including multiple conspecifics packed like sardines?

    • They are schooling fish in the wild and having others around will make them more comfortable. In a small tank it is essentially trapped inside a small box by itself. Just imagine yourself as a fish… which would you prefer? It’s a simple answer…

      • I don’t buy the tang police argument. There are plenty of stressors in the wild that a fish won’t see in a captive environment. i.e. The need to constantly look over your back to see if another fish is about to eat you would rank as high stress.

        Tangs like other “scaleless” fish such as the freshwater clown loach are susceptible to parasitic infection, marine ich being the NUMBER 1. In my experience I have found that the manner in which captive marine fish are captured, transported and held in large holding tanks is a much larger contributor to the demise of any given fish. Look at your local Petco store. It takes in new marine fish each week and places them into the same ich contaminated tanks. The tanks are never treated for ich (copper/formalin) and the cycle continues forever.

        Simply put: Marine ich along with other parasitic infections is “epidemic” to the ornamental fish industry. As long as the industry remains profitable by passing the loses on to the consumer your not going to see any changes.

        • David Bowers says

          Fred, you raise some good points of conversation. Of course fish are stressed in the wild. I believe however: (do not have direct evidence for) but believe the stresses are at natural levels. Collecting fecal pellets with Dr. Turner at UT, we determined cortisol levels of parrot fish in what we classified as “healthy” reefs. Meaning there were good populations of both fish and coral. We found the stress hormone levels to be low and near constant throughout the year and between years. Unnatural forces such as over fishing and pollutants resulted in elevated cortisol which never return to the levels found with fish on healthy reefs.

          It is a leap to apply those findings to an entirely different genius of fish, Yet I can not help but be at lease rather suspicious that our tang fish friends are responding is similar ways.

          Again very few creatures ever die of stress directly; but stress compromises the immune system (found true in nearly all vertebrates). Stress also physically changes creatures’ genetics (but that is an entirely different conversation)

          The closer we can be to natural conditions I would suppose, the lower the stress level will be for any fish and the more likely that fish will be to withstand disease (regardless of it being ick or any other threat)

          • David,

            In the interests of full disclosure I’d first like to say that all that I say is without proof, as are most posts that are found in this group as well as others. Proof costs money and time and as the average hobbyist I have neither. I do however feel I was blessed with a fair degree of common sense and intelligence.

            No doubt that stress affects health regardless if your a fish or a person. Stress can be chronic or acute. In the case of acute stress elevated levels of cortisol and adrenaline are a good thing since it helps the animal swim or run faster from an attacker.

            I don’t believe you can simply make a statement that X gallons of aquarium are required for Y tang without taking a lot of other things into consideration. I also don’t believe that tangs have a tape measure tucked away under their fins or know how to use one.

            Example: Put a Strawberry Dottyback with a bad disposition into any size tank and that one small fish is going to cause a LOT of stress to all the other inhabitants. Stress is stress regardless the source.

            Based on the lack of actual fact concerning marine fish and tank size I put my faith into observation. Right now I’m looking at my tangs, which are not housed in the recommended tank size and they all appear very “happy”. They are fed well, have their own safe places and don’t show any aggression towards each other. Their main interest is in feeding.

            There is plenty of information about this hobby and others floating around, the majority of which is not based on any fact/proof and in some cases is outright wrong. Some people blindly and without any thought simply do as they see others do whether it makes any sense or not. Example: I saw one individual post that his X fish which he was also told was “reef safe” was eating his LPS. In the same post he also stated that he was told only to feed his fish once every three days in the interest of water quality. My guess is that the fish was starving and when it came to the choice of starvation or LPS the fish decided to go for the LPS.

            I also believe that money drives a lot of things in this hobby. “Got a problem? Buy this gadget…” People seem to rather fork out the money rather than do a little bit of reading.

            If marine hobbyist are really concerned about tang swimming room they should simply not buy them since your never going to duplicate the size of an actual reef.

  4. Another great great article. The tang police is a real and necessary thing. :p

  5. Matt Carroll says

    Great article. The misinformation floating around the hobby is in full evidence even here in the comments! 🙂

    I don’t disagree with any guidance in the article. IMO, detritavores like Kole tangs (Ctenochaetus sp.), which tend to operate solo in the wild, can be almost ideal tank residents, just as you described. The Zebrasomas (i.e. Yellow Tang) and especially the Acanthurus (i.e. Achilles Tang) tangs are the opposite. While it’s certainly possible to get a specimen to adapt somewhat to captivity, the cases I’m aware of where these fish are alive at year 5+ are practically unknown. It’s essentially impossible to state “minimum requirements” for an oceanic fish – even if they do hang out, sometimes solo, on a reef during meal times!

    • Bobby green says

      My yellow tang is over 15 years old my coral beauty is 13 years old i also have a 15 year old blue damsel i cycled my tank with 15 years ago. I have a 150 gallon 6ft tank ive always quarantined my fish and corals ive got over 250lbs of live rock set up with the tang in mind lots of caves and tunnels. I keep it stocked light and most of my fish will let me touch them, when i stare in the tank they all group together and stare back. I also dont starve my fish because im to lazy to do a water change. Its not hard to keep fish healthy for many years you just cant be lazy about it, you dont starve your dog or cat by feeding it twice a week like ive heard people recommend for fish……a fat fish is a healthy fish

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