Doctorfish Care: Acanthurus chirurgus

At first glance, you might not think much of a doctorfish. They have the usual tang shape (a flat rhomboid). But it doesn’t stand out much. You tend to find them in blueish gray or brown colors with 10-12 dark bands on the sides. Other than those bars, the only ornamentation is a blue ring around the “scalpel” at their caudal peduncle. (The spine for which every surgeonfish gets its name) Not as impressive when you’ve seen some of the brighter tangs darting around the reef.

But then a doctorfish moves from a reef to the sand, and you see it: the color shift! The darker brown shades switch to paler blue (or vice versa if the fish moves the other direction). Or perhaps a male in the group flashes a brighter hue to assert dominance. You could even watch the school change color when they spot a potential predator, bringing attention to that spine at their tail. It’s one of the more remarkable details of this tang species.

These tangs accomplish the color-changing abilities through iridophores in their scales. All fish possess these specialized chromatophores (color pigments) to varying degrees. The iridophores control the amount of reflection or “sparkle.” As they open or close, the doctorfish becomes brighter (blue) or darker (black). They use the shifts in color for communication within the school and represent mood when housed alone in a tank.

The stripes on their side help differentiate them from other tangs with that blue or dark base shade. And, of course, so does the highlighting around the scalpel. They use the spine for defense against predators and to engage in fights for dominance. YOU need to keep it in mind whenever you handle the fish. Wounds from a slash can result in swelling and possible infection (to say nothing of the pain!).

Doctorfish spread out across the Atlantic and into the Gulf of Mexico. Divers and anglers often spot them schooling alongside ocean tangs (Acanthurus bahianus). If you venture into shallower reef habitats, you’ll probably encounter one (well, more than one – they’re usually in impressive shoals).

In Panama and the Bahamas, scientists have recorded doctorfish at ages of 16-27 years. And some think they survive for up to 43 years – provided they don’t suffer high levels of stress. Of course, those are WILD lifespans. In the home aquarium, they usually only live for around 7-8 years (even with the best care).

Creating the Ideal Doctorfish World

Doctorfish pop up as far north as Massachusetts and as far south as Brazil. If you head east, you’ll spot them along the tropical coast of Africa. And they’re popular fish throughout the reefs of the Gulf of Mexico and the Caribbean. They forage along seagrass beds and over shallow rock and coral reefs (nothing deeper than 130 feet/40m). It’s not surprising to find these striped tangs in the company of other tangs and schooling fish.

If you want to add a doctorfish to your reef tank, you won’t need to fret over much. The one thing all of those regions have in common is SPACE. These surgeonfish need room to swim. In the wild, they spend the daylight hours exploring corals and sand in search of food. And you need plenty of open swimming room for them to do the same in your tank.

Those nooks and crannies need to accommodate the adult size of your doctorfish, too. Whether you choose to have a fish-only tank (popular when you’re dealing with surgeonfish of this size) or a reef tank, keeping the stress level low by offering places to hide will improve the overall health of your fish. They don’t produce a thick mucus coat, and that leaves them vulnerable to infection. You want them to stay comfortable and happy.

Doctorfish Tank Size

On the surgeonfish size scale, doctorfish come out near the top. They average around 12 inches (30.5cm) in length as adults. With the proper living conditions, you can see a maximum length of 14 inches (35.6cm). And since you need to offer as much room to swim as possible, that means providing a suitable aquarium size.

You shouldn’t go smaller than 100 gallons (379L) – and that’s for ONE of these striped tangs. Most hobbyists don’t choose to keep more than one at a time (we’ll get to that in a minute), so it’s usually not a problem. If you want to attempt to set up a school, you’ll need to increase the planned size of the tank. Tangs ALL have an aggressive streak buried in their DNA. If you don’t allow everyone to have space, you’re asking for problems with bullying down the road.

Are Doctorfish Reef-Safe?

Doctorfish possess specialized teeth that allow them to “comb” algae away from rock and other surfaces. This makes them ideal for keeping in reef tanks. And since they’re not interested in targeting coral polyps, you don’t need to worry about harm to your SPS or LPS additions. It’s one of the reasons aquarists find them a pleasant addition.

However, you need to keep an eye on your invertebrates. Algae-eaters they may be, but they’re omnivores, not herbivores. And there’s nothing they like more than a delicious mollusk. You might find them attempting to pry your mussels or clams open. Or they could start eyeing some of your smaller crustaceans.

As long as you keep your doctorfish well-fed, it shouldn’t be a problem. You should still keep this in mind when setting up your aquarium, though.

Doctorfish Diet

But doctorfish aren’t herbivores; they’re omnivores. So they’ll also need protein sources to keep their active metabolism running. Small quantities of food 2-3 times a day work best to prevent them from eyeing up their tank mates. You can use commercial fish foods, or you can offer frozen or live foods:

Doctorfish swallow food whole. Those special teeth? They don’t work for chewing. So these tangs possess an organ in the intestinal tract that functions like a gizzard (you got it – like a bird). Filled with sand particles, it grinds the food down to make it easier to digest. So while you SHOULD consider the size of the portions you add to the tank, you don’t need to go overboard with your chopping.

Doctorfish Behavior and Tank Mates

In the wild, doctorfish graze in schools. They space out over seagrass beds and coral reefs, picking through the rocks and sand. You’ll often find them in the company of other fish, as you can see in this YouTube video from Akumal Bay, Mexico:

As youngsters, doctorfish show up at cleaning stations – as cleaners. They remove parasites and algae from green turtles. You’ll often spot them working around the head, flippers, and all along the shell.

You won’t see the same change if a doctorfish pulls up to a cleaning station operated by shrimp, though. This is because shrimp use touch to work, not sight.

Unfortunately, the comradery noted in the wild doesn’t carry through to home aquariums. Unless you set up a MASSIVE tank – complete with plenty of room for everyone to establish their territory – it’s best to only keep ONE doctorfish. They don’t get along with one another in the captive environment.

Unlike most tangs, though, you CAN keep doctorfish with other Acanthurus species. That part of their programming seems to remain intact. They have a moderate temperament and tolerate fish they’d typically hang out with on the reef. This includes:

• Angelfish
• Anthias
• Clownfish
• Damselfish
• Gobies
• Triggerfish (ONLY if planktivores)

You want to move carefully with any other algae-eaters. While doctorfish don’t strictly feed on algae, they’ll get aggressive if they feel the food’s in short supply. And adding the tang LAST will help diffuse potential bullying before it has a chance to start.

Breeding Doctorfish

Doctorfish males and females look the same. This doesn’t present much of an issue, as getting the species to spawn in a captive setting doesn’t usually happen. And that’s because you need a group (and they’re not exactly fond of one another in the aquarium).

This tang spawns in a group during the late evening. The fertilized eggs drift on a single drop of oil for 24 hours before hatching. The acronurus larvae emerge and join the active part of the plankton. These translucent larvae look NOTHING like the adults. Stumbling upon the larvae in the plankton, scientists initially thought the diamond shape, HUGE eyes, and prominent pectoral fins represented a separate genus of fish. It took watching the development into juvenile doctorfish to realize the error.

It takes around a week for the larvae to metamorphose into juveniles. They then drift into shore and settle onto the reef. And that rapid growth continues. By the time the young doctorfish are nine months old, they’re sexually mature.

Who doesn’t love a fish that changes color? Doctorfish bring plenty of cool details with them to reef tanks. They also present a few challenges. And you’ll need to decide whether the good outweighs the bad.

Pros

• Doctorfish possess teeth adapted to pulling algae off rock and coral, helping keep tanks clean.
• By changing the color of their scales, doctorfish can highlight an area afflicted with parasites to guide cleaner fish to the problem.
• Doctorfish may not get along well with each other, but they tolerate most other tangs nicely.

Cons

For More Information

Maybe doctorfish don’t have dazzling patterns or even dramatic sizes to recommend them. Does that mean they aren’t worth considering for your aquarium? Of course not. With a “gizzard” and the ability to change color, how could you resist? To seal the deal, though, let’s dive into some more information.

This YouTube video shows a school of doctorfish in their “subdued” coloring in Puerto Moreles, Mexico:

Want to know about some of the best doctorfish tank mates?

Or maybe you’d like to consider some of the flashier tangs out there:

Conclusions

Do doctorfish have a fairly benign name? (For a surgeonfish, anyway) Maybe. And is it possible to overlook them out on a reef? Sure. But when you spend enough time watching for that color change, they turn interesting. And getting to see a fish pulling up to your aquarium’s cleaning station? Nothing beats that. Oh, sure, you won’t get to keep more than one (unless you have a room-sized tank), but even one fish with a cleaner shrimp is worth it, right?

References