The Lavender Tang, Acanthurus nigrofuscus, also known as the Brown Surgeonfish, has a disk shaped body, very similar looking to other Acanthurus species. Though being the smallest and least colorful species in this genus, it is easily recognized by the dull orange spots on the head and the two dark spots at the rear base of the dorsal and anal fins. Adult coloration varies from a brown to a light grayish brown featuring a lavender color on the fins. When stressed or displaying aggression, its entire dorsal fin and upper back lighten in color, sometimes becoming noticeably yellow. Also featuring blackish brown lips, its pale pectoral fins are narrowly edged in black, and at times, the anal fin is narrowly edged with white, with a crescent shaped caudal fin. On each side of the caudal peduncle is a single spine or "scalpel" used for defense or dominance, hence the Surgeonfish reference. The spine is folded down into a groove that is circled in black when not in use. Caution should be used when handling Surgeonfish as a cut from its scalpel can cause discoloration and swelling of the skin with a high risk of infection. The pain lasts for hours then still ends up having a dull ache. Juveniles are brown to bluish black and have orange scribbles on the head that break up into spots as they mature.
The Lavender Tang can grow to be about 8" and requires a tank no less than 130 gallons as a fully matured adult. A minimum 60 gallon tank will be OK temporarily for a juvenile, as they are rather slow growers, but keep in mind that too small of an environment can stunt their growth and they can develop 'behavior issues'. Like most other Surgeonfish or Tangs, the Lavender Tang likes water with a moderate to heavy flow, creating currents to swim in. Being very active during the day, they require a large tank with plenty of open room to swim about while also providing plenty of live rocks and or Corals to offer some cover if frightened, and to sleep in at night. Lush natural algae growth in the tank is suggested in order for the Tang to be able to graze upon in between meals. They may also jump out of an open aquarium, so be sure to have a tightly fitting lid.
Being a peaceful fish in nature, it will get along with most other peaceful tank mates, and should not be housed with aggressive fish. They can even be kept with a variety of tank mates including some of the other genus' of Surgeonfish, though it will be aggressive towards others of its own kind. Unless you have a huge system, like a few hundred gallons or so, it is best to to keep only one Lavender Tang per system. Like all Tangs, they do not have scales to help protect them, they also do not produce as much skin mucus on their bodies as other fish, making them susceptible to diseases such as Marine Ich and Marine Velvet. Fortunately the Lavender Tang is very tough and is not as likely to develop Marine Ich as many of the other species. However, they are definitely a candidate for quarantine when you first receive them. They can be treated successfully with copper based medications, but because they have an important microfauna in their digestive system, prolonged or continuous use of a copper treatment is not advised. Keeping Neon Gobies or Cleaner Shrimp will help by providing a cleaning service for the Tang, allowing for better health overall.
It can be difficult to get the Lavender Tang to eat at first, as they can be very shy. Keeping naturally growing algae in the tank will help with this, along with blanched lettuce and brine shrimp to entice it to eat. It is also known that pellets soaked in garlic may help fend off Marine Ich, as well as entice it to eat. When you notice your Tang is more comfortable in it's environment, you may offer a variety of algae based foods for the main part of it's diet, along with some meaty foods. Once acclimated and it becomes accustom to aquarium foods they are quite hardy and long lived. Their diet should consist of natural algae, as well as prepared frozen formulas containing algae or spirulina. Japanese Nori or other seaweed can be offered by attaching it with a vegetable clip to a rock or the glass. Vitamin enriched frozen brine and mysis shrimp should also be offered to help with a balanced diet. Live rock with heavy algae growth is ideal, as it will allow the Tang to scrape it teeth along the rock. Feed at least 3 times daily, in smaller amounts instead of a large quantity once a day. This will help with higher water quality over a longer period of time. They will thrive in a temperature range of 74 - 82° F and a pH of 8.1-8.4.