Gem Tang: Species Profile & Ultimate Care Guide

| Updated: June 14, 2023
Gem tang under white lights in a reef aquarium

If you are looking for stunning and rare fish to add to your reef tank, you might want to consider the Gem Tang. This fish is one of the most prized specimens of all saltwater fish for its striking color and contrast and is also one of the most desirable Tangs for the reef aquarium. However, before you decide to splurge on this gem (pun absolutely intended), you should know some important facts about its care, diet, behavior, and origin. In this article, we will provide you with a comprehensive guide on everything you need to know about the Gem Tang and help you decide if this fish is right for you.

Species Overview

Scientific Name
Zebrasoma gemmatum
Common Names
Gem Tang, Gemmatum Tang, Mauritius Tang, Spotted Tang
Acanthuridae (Surgeonfishes)
Western Indian Ocean, especially Mauritius
Adult Size
Up to 8.7 inches (22 cm)
Life Expectancy
About 30 years in captivity
Moderate, territorial and intolerant of conspecifics
Moderate, requires large tank, high water quality, and varied diet
Minimum Tank Size
180 gallons for one, 300 gallons or more for multiple
Captive Breedable

What is a Gem Tang?

The Gem Tang (Zebrasoma gemmatum) is a marine reef tang in the fish family Zebrasoma. They are also known as Gemmatum Tang, Mauritius Tang, or Spotted Tang. They have a disc-shaped body with a dark blue background and a galaxy of tiny white spots. They also have bright yellow accents on their fins and tail, which add a burst of color to their appearance. They can grow up to 8.7 inches (22 cm) in length and have a lifespan of about 30 years in captivity.

Gem Tangs are native to the western Indian Ocean, where they are found in coral reefs at depths of 33-200 feet (10-61 m). They are particularly abundant, comparatively, around Mauritius, an island nation off the coast of Africa. They prefer areas with strong water currents and plenty of live rocks to graze on algae.

Why is the Gem Tang so Expensive?

The Gem Tang is one of the more expensive saltwater fish in the market, with prices ranging from around $400 to $2,000 or more depending on the size and quality of the specimen. Fortunately, these prices have come down quite a bit; several years ago, they were a minimum of $2000. Still a pretty expensive fish, though. There are several reasons why this fish commands such a high price tag:

  • The Gem Tang is very rare and hard to find in the wild. They do not swim in large groups, and they inhabit areas that are difficult to access by divers and collectors. They are also protected by strict Mauritius regulations, limiting the number of fish exported annually.
  • The Gem Tang is very delicate and sensitive to stress. They require careful handling and transportation from their natural habitat to the holding facilities and then to the final destination. They are prone to infections and diseases if they are exposed to poor water quality or incompatible tank mates. They also need a lot of space and hiding places in their tanks to feel comfortable and secure.
  • The Gem Tang is very popular and in high demand among hobbyists and collectors. They are considered a status symbol and a sign of prestige among reef enthusiasts. They are also admired for their beauty and uniqueness, as no two Gem Tangs have the same pattern of spots. Some people even look for specific variations, such as the Barcode Gem Tang, which has vertical stripes instead of spots.

Caring for a Gem Tang

If you are willing to invest in a Gem Tang, you probably want to provide it with the best possible care and environment. Here are some tips on how to keep your Gem Tang healthy and happy:

Tank size

The Gem Tang needs a large tank with plenty of swimming space and water movement. The minimum tank size for one Gem Tang is 180 gallons (681 liters), but bigger is always better. If you want to keep more than one Gem Tang, you will need at least 300 gallons (1136 liters) or more, and make sure they are introduced at the same time to avoid territorial disputes.

Tank setup

The Gem Tang is reef safe and compatible with most corals and invertebrates. However, they need plenty of live rocks with algae growth for them to graze on throughout the day. They also need lots of hiding places and caves where they can retreat when they feel threatened or stressed. You should also provide them with adequate lighting, filtration, skimming, and water changes to maintain optimal water quality and parameters.


The Gem Tang is an herbivore that feeds mainly on algae in the wild. In captivity, you should supplement their diet with various types of seaweed, such as nori, spirulina, or wakame. You can use a veggie clip or a rubber band to attach the seaweed to the rocks or the glass of the tank. You should also offer them some high-quality marine flakes or pellets that are specially formulated for herbivorous fish.

Occasionally, you can treat them with meaty foods like mysis shrimp, brine shrimp, or krill. You should feed your Gem Tang at least twice daily and ensure they get enough food to prevent them from becoming malnourished or aggressive.

Diseases in Gem Tangs

The Gem Tang is susceptible to various diseases and parasites that can affect their health and appearance. Some of the most common ones are:

  • Ich: A parasitic infection that causes white spots on the skin and gills of the fish. It can also cause breathing difficulties, loss of appetite, and lethargy. It’s highly contagious and can spread quickly to other fish in the tank.
  • Marine Velvet: Another parasitic infection that causes a fine dust-like coating on the skin of the fish. It can also cause rapid breathing, scratching, and clamped fins. It’s very deadly and can kill your fish within days if left untreated.
  • Lateral Line Erosion: A condition that causes the erosion of the lateral line and the scales along it. It can also cause ulcers, infections, and loss of color. It’s usually caused by nutritional deficiencies, especially vitamin C and iodine.

How to Breed Gem Tangs?

The Gem Tang is very difficult to breed in captivity, as they have complex mating behaviors and requirements. They are protogynous hermaphrodites, which means they are born as females and can change into males when needed.

They form harems of one male and several females in the wild and spawn at dusk during the full moon. They release their eggs and sperm into the water column, where they are fertilized externally. The eggs hatch into planktonic larvae that drift with the currents for several weeks before settling into the reefs.

There have been very few successful attempts to breed Gem Tangs in captivity, as they require large tanks with precise water conditions and lighting cycles. They also need live foods like rotifers and copepods to feed their larvae.

One of the most notable breeding successes was done by Bali Aquarich, a breeding operation in Indonesia that managed to produce several batches of captive-bred Gem Tangs in 2016 and 2017. They used hormone injections to induce spawning in their broodstock and raised the larvae in separate tanks with live foods and green water. They sold their offspring for $1,500 each, which was substantially cheaper than wild-caught specimens at the time.

Where to Buy a Gem Tang?

If you are interested in buying a Gem Tang for your reef tank, you should be prepared to spend a lot of money and do a lot of research. You should look for reputable sources that can provide healthy and well-acclimated specimens legally collected and exported from Mauritius.

You can also check your local fish stores or ask around with fellow hobbyists who might have a gem tang for sale or trade. However, you should be careful and inspect the fish carefully before buying them, as they might be unhealthy, injured, or misidentified.

Is the Gem Tang Right for You?

The Gem Tang is a breathtaking fish that can add a lot of beauty and value to your reef tank. However, they are not for everyone, as they require a lot of care, attention, and money. You should only consider getting a Gem Tang if you:

  • Have a large, well-established reef tank with plenty of live rocks and algae.
  • Have experience in keeping saltwater fish and maintaining optimal water quality and parameters.
  • Have the budget and the willingness to spend thousands of dollars on a single fish.
  • Have the patience and dedication to provide your Gem Tang with a varied and balanced diet and regularly monitor its health and behavior.
  • Have the space and the compatibility to keep your Gem Tang with other peaceful and reef-safe fish or with other Gem Tangs if you have a big enough tank.
  • Have the passion and the appreciation for this rare and unique fish and are ready to enjoy its beauty and personality for many years to come.

If you meet all these criteria, then congratulations! You are ready to welcome a new pet into your life. The Gem Tang is a gem indeed, and you will not regret having one in your tank.

Final Thoughts

We hope this article has given you some useful information and insights on the Gem Tang, one of the most sought-after saltwater fish in the world. They are truly amazing creatures that can bring a lot of joy and satisfaction to any reef enthusiast. The downside is they are very expensive and demanding and require great care and responsibility. The Gem Tang is not just a fish; it is an investment, a commitment, and a treasure.

Thank you for reading this article. We hope you enjoyed it and learned something new. If you have any questions or comments, please feel free to leave them below. We would love to hear from you.

Happy reefing!

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