Gem Tangs can be found in the Western Indian Ocean off the coast of Mozambique, South Africa, Madagascar, and near the islands of Reunion and Mauritius. These tangs live in surge areas, thus making them harder to collect and less common. These rare tangs are a dark bluish black with several tiny white spots. They have bright yellow on their fins and tail. They will use their spines as a weapon against other fish that threaten them. The Gem Tang can reach up to 8.5 inches in length and requires an aquarium of at least 100 gallons with live rock and plenty of room to swim.
Tangs, in general, are primarily herbivores. They need rocks to graze on as their diet is primarily marine algae. For tanks on the smaller side that have less live rock to grow algae, you will need to supplement your tang’s diet with Nori or other vegetable matter like Nori, Romaine lettuce, spinach leaves, or broccoli. They also will accept flake foods and sometimes small meaty offerings like Mysis shrimp. A good variety of foods will keep your tang healthy and vibrant. A well-fed tang won’t pick at your corals, but there is always a possibility if there is no algae or Nori present. Also, a well-fed tang has less chance of developing HLLE (Head and Lateral Line Erosion). HLLE can be fatal depending on severity and can leave lasting scars on the tang.
As stated earlier, a Gem Tang can reach up to 8.5 inches and requires an aquarium of at least 100 gallons with live rock and plenty of room to swim. Tangs, in general, will spend their days swimming from one side of the aquarium to the other, picking on any algae growing on your live rock or frag plugs. In the ocean, tangs swim great distances every day. This should give you an idea of how much swimming space a tang will need to be satisfied in your tank. It is also recommended that your tank be wider than it is tall, to allow them more space to swim. Without ample space to swim, a tang can become stressed and will be very prone to diseases like Ich.
Gem Tangs can be very aggressive to other tangs of the Zebrasoma genus, but are usually peaceful with fishes and non-Zebrasoma tangs after they establish their place in the pecking order of the tank. With the spines built into their tails, they are usually at the top of that pecking order. Keeping your Gem Tang well-fed will reduce aggression in your reef. If you intend to keep fish, a netted lid is recommended.