Nutrition, Diseases, Tank Size and Mates

Gem Tangs come at a high price because they are not easy to find and transport, so knowing the proper care for these beautiful fish is essential. In this guide, you will learn everything you need to succeed with this top of the line fish from diet and tank configuration to breeding challenges and common diseases and prevention. So, without further ado, let’s dive in!

Species Summary

Known scientifically as Zebrasoma gemmatum, the Gem Tang or Spotted Tang, is a breathtaking saltwater fish native to the western Indian Ocean. Gem Tangs have flattened, disc-shaped bodies with dark blue and a galaxy of tiny white spots with bright yellow accents on the fins and tail. They are generally active swimmers and have inquisitive natures, often examining live rock for new signs of algae growth.

However, Gem Tangs can show aggressive behavior towards other tangs that may be introduced into their aquariums. The Gem Tang is one of the most expensive fish in the saltwater hobby, with prices ranging from around $800 to $1500 and sometimes more!


A Gem Tang’s body resembles a flattened disc with a triangular-shaped head and a small, pointed mouth. Their color is blue-black with white dots and a yellow tail. They have the same “scalpel” (protective tip) as other members of the Tang family and make an eye-catching addition to any reef aquarium. Juvenile tangs don’t have the same vibrant colors as adults, this is something they will acquire as they continue to mature.

A Gem Tang swimming in a saltwater aquarium


The lifespan of the Gem Tang can be up to 25 years in the wild and 7-10 years in captivity. However, providing the best care possible, combined with a nutrient-dense diet, can result in a longer lifespan.


The Gem Tang can reach a size of 8.7 inches or 22 centimeters. Juveniles are usually about 2-3 inches long when they first arrive in the aquarium.

Author’s note: It is important to keep in mind that even though they are small, they still need plenty of room to swim due to their active nature, so a larger aquarium is recommended.

Gem Tang treatment

If you are installing a tank for your Gem Tang, you will want information about their needs. It is very important that you have a tank large enough for them to swim and feed in, with the correct temperature, lighting and water filtration.

Next, we’ll talk about some important factors in creating the best environment to ensure your new beauties thrive in their new home.

tank size

The recommended average tank size for a 180 gallon Gem Tang. These very active fish need a lot of space to swim. Like other varieties of Tang, they can often show some aggression towards other fish, so having a large tank is necessary unless you plan to house them alone.

Water parameters

  • Water temperature: 72°F-78°F
  • pH levels: 8.1-8.4
  • Water hardness: 420ppm
  • Specific gravity: 1.020-1.025

Tank configuration

Gem tangs are attractive fish that thrive in aquariums when the conditions are right. It is very important to make the environment as stress-free as possible for these fish. They are relatively easy to maintain, but there are some specific things you need to consider when setting up a tank for them.


Lighting your aquarium is very important. The most recommended lighting is LED lights. There are different strengths and different settings to change the look of your underwater world.


These fish are known to be quite messy eaters, so a good filtration system is a must. A combination of biological, mechanical and chemical filtration is recommended to maintain good water quality in a reef aquarium with Gem Tangs.


When acclimating a Gem Tang to an aquarium, it is important to do so slowly to reduce stress levels. One way to do this is to add tangs to an aquarium last. You should also slowly introduce new tangs with other tangs to keep everyone happy.

Are Gem Tangs Reef Safe?

Yes, Gem Tangs are safe for reef aquariums. They graze on live rocks and algae and are compatible with other types of fish. They don’t eat your coral and like to hide in the nooks and crannies between the rocks.

Possible common diseases and prevention

Gem Tangs, like other marine fish, are susceptible to various diseases. Here are some common illnesses and prevention methods to help maintain the health of your Gem Tangs:

  • Ich (Cryptocaryon irritans): This is a common parasitic infection that appears as small white dots on the body of the fish. To prevent this disease, quarantine any new fish or coral for at least 2-4 weeks before introducing them to the main tank. Also, maintain good water quality and minimize stress levels in the tank.
  • Sea Velvet (Amyloodinium ocellatum): A highly contagious parasitic disease that appears as a fine golden or brown dust on the fish’s body. Prevention methods include quarantining new arrivals, maintaining good water quality, and using a UV sterilizer to kill free-floating pests.
  • Lateral Line Erosion (Head and Lateral Line Erosion – HLLE): This condition is characterized by pitting and erosion along the lateral line and head of the fish. To prevent this, provide a varied diet rich in vitamins A, C, and D, maintain optimal water quality, and minimize stress in the tank.
  • Bacterial Infections: Various bacterial infections can affect Gem Tangs, resulting in open sores and discolored patches on the body. To prevent bacterial infections, maintain good water quality, avoid overcrowding, and provide a stress-free environment.
  • Internal parasites: These can cause weight loss, lack of appetite, and abnormal bowel movements. To prevent internal parasites, quarantine new fish and feed them high-quality, parasite-free food.

Overall, prevention is key to maintaining the health of your Gem Tangs. Focus on providing a clean and stable environment, proper nutrition, and quarantine procedures to reduce the risk of disease in your aquarium.

Author’s note: Regular water changes, testing of water parameters, and monitoring of fish behavior can help you catch any problems early, allowing for prompt treatment and preventing the spread of disease.

Food and diet

Gem Tangs are primarily herbivores with omnivorous tendencies, so a plant-based diet with the addition of some protein will suffice their dietary needs.. In captivity, it is important to provide them with a varied diet that mimics their natural eating habits. Here are some ideal food options for Gem Tangs:

  • Seaweed: Gem Tangs love to graze on dried seaweed, which is readily available at pet stores. You can tie the seaweed to a clamp or use vegetable tongs to hold it in place. If your pet store is out of seaweed, the nori sheets can be cut in small trips and replaced.
  • Pellets: A high quality pellet food specially formulated for herbivorous fish is a great option for Gem Tangs. Look for pellets that contain spirulina, algae, and other herbal ingredients.
  • Frozen Foods: Frozen foods like Mysis shrimp, brine shrimp, and krill are also good options for Gem Tangs. You can mix them with other plant-based foods to create a varied diet.
  • Vegetables: Certain vegetables like spinach, zucchini, and broccoli can be blanched and cut into small pieces to feed Gem Tangs.

Author’s note: It is important to feed Gem Tangs in small amounts several times a day rather than one large meal once a day. This will help prevent bloat and ensure the fish are getting proper nutrition.

Last but not least, Gem Tangs should not be overfed. This can lead to health problems. Providing a varied diet will help ensure that Gem Tangs receive all the nutrients needed for their health and well-being.

A Zebrasoma gemmatum looking for food

Behavior and temperament

These beautiful aquatic creatures spend a lot of time swimming as they are very active. They are not as aggressive as other types of Tangs, but are best kept with a diverse population in their tank. They may get along well with your other fish, but make sure you don’t put them in an aquarium with fish that look like them.

Gem Tang Tank Mates

For the most part, Gem Tangs are peaceful fish. They just tend to have problems with others like them. Choose fish from this list of compatible tank mates when setting up your aquarium.

  • Lawnmower Blenny
  • Midas blenny
  • Tail blenny
  • firefish goby
  • neon goby
  • Yellow Guardian Goby
  • Yellow coris wrasse
  • Snowflake Clown Fish
  • Pink Skunk Clownfish


Breeding Gem Tangs in captivity is no easy task.. On the one hand, it is difficult to distinguish the female from the male. Due to the sharp point on their back, handling them is also difficult. Another reason breeding is difficult is that the male and female were “making” their eggs. It is not known how long they take to develop.

One of the reasons these fish are so expensive is that they have never really been successfully bred in captivity. They are rare and beautiful fish that really thrive in the wild. Recreating this same environment in an aquarium is not as simple as one might think. I

Author’s Note: Breeding a Gem Tang isn’t necessarily impossible, but most Tangs are wild-caught, which should give you a clue as to the breeding success rate.


Overall, taking care of Gem Tangs requires commitment and attention to detail. With proper care, these beautiful fish can live a long and healthy life in your aquarium. If you are considering making the big investment to add the Gem Tang to your collection, we strongly recommend that you do your research and prepare ahead of time to ensure a successful and enjoyable experience for you and your fish.

We hope this guide has answered all your questions and don’t forget to hit us up on Facebook to share how things are going. Good luck!

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