The yellow tang (Zebrasoma flavescens) is a very popular saltwater fish, most likely due to its bright yellow coloration and distinct shape. As a member of the surgeonfish family, it possesses small white spikes on the sides of its tail, which it uses to attack other fish. Under normal conditions, the two spikes are held flat against the tail, but when provoked or fighting over territory, the spikes are extended and the tang will slap the other fish with its tail to stab it.
With that said, it is a very territorial fish and should be the only tang in the tank if you only have a 55 gallon or larger tank. Sometimes it is OK if you add two tangs simultaneously, but you really shouldn't have two tangs in that small of a tank anyways. Although it often schools in the wild, the yellow tang needs its space in an aquarium and will defend it to the death.
I was able to house my yellow tang with some smaller fish without issue, but it was occasionally seen chasing the smaller fish behind the rocks. It never attacked any of them, and for the most part it swam around them without any aggressive behavior. If you have a bigger aquarium, like a 150 gallon tank, you can usually house multiple yellow tangs without issue, but make sure they have plenty of space and rock to claim.
As evidenced by the elongated snout, this fish is a herbivore and will eat some types of macroalgae, but it will also eat seaweed sheets and herbivore pellets and flakes. It is diurnal, so it is active during the day and sleeps at night. At night or when stressed, it will become pale and display a brown horizontal stripe on its side as a sort of camouflage. This helps it to hide among rocks and coral when a predator approaches.
A yellow tang can get fairly large, sometimes approaching a foot in length. Therefore, it should not be kept in anything smaller than 55 gallons for long periods of time. Many people say 75 gallons is the minimum and I tend to agree. Tangs are susceptible to waterborne parasites like ich, but the yellow tang is one of the hardier tangs and I had no problems with the disease.
In summary, this fish is a great herbivore that will make an excellent addition to any saltwater aquarium that is 55 gallons or larger. However, if you are looking for something that will eat a lot of macroalgae, you may be better off getting a foxface rabbitfish since the yellow tang will not usually eat everything that grows on your rocks. Nonetheless, it is a beautiful fish and adds a lot of color to the tank with its bright yellow body. It is easy to care for and should live a long time as long as you maintain appropriate tank conditions.