Gem Tang Care: Nutrition, Diseases, Tank Size & Mates

Gem Tangs have a high price tag because they are not easy to find and transport, so it is essential to know the proper care of these beautiful fish. In this guide, you will learn everything you need to succeed with this high-end fish from diet, and tank setup 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 originating from the western Indian Ocean. Gem Tangs have flattened, disc-shaped bodies with dark blue and a galaxy of tiny white spots with vibrant yellow accents on the fins and tail. They are generally active swimmers and have an inquisitive nature, often examining live rock for new signs of algae growth.

However, Gem Tangs may 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 about $800 to $1500 and sometimes more!


The body of a Gem Tang resembles a flattened disk with a triangular-shaped head and a small, pointy mouth. Their color is blue-black with white dots and a yellow tail. They have the same “scalpel” (protective spike) as other members of the Tang family and make an eye-catching addition to any reef tank. Juvenile tangs don’t have the same vibrant colors as the 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 to 10 years in captivity. However, providing the best care possible, combined with a nutrient-rich diet can result in longer life expectancies.

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Average Size

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

Author Note: It is important to keep in mind that while they are small, they still require a lot of swimming room due to their active nature, so a larger aquarium is recommended.

Gem Tang Care

If you’re setting up a tank for your Gem Tang, you’ll want to get some information about their needs. It’s very important that you have a tank that is big enough for them to swim and forage in, with the appropriate water temperature, lighting, and filtration. 

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

Tank Size

The average recommended tank size for a Gem Tang 180 gallons. These very active fish require a lot of room for swimming. Like other varieties of Tang, they can often display some aggression towards other fish, so having a large tank is necessary unless you’re planning to house them alone. 

Water Parameters

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

Tank Setup

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 keep, but there are some specific things you should consider when setting up a tank for them.


Lighting in your aquarium is very important. The best-recommended lighting is LED lights. There are different strengths and different settings to change the look and feel 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 into an aquarium, it is important to do so slowly to reduce stress levels. One way to do this is by adding tangs into an aquarium last. You should also introduce new tangs with other tangs slowly to keep everyone happy..

Are Gem Tangs Reef-Safe?

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

Common Possible Diseases & Prevention

Gem Tangs, like other marine fish, are susceptible to various diseases. Here are some common diseases 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 fish’s body. To prevent this disease, quarantine any new fish or corals for a minimum of 2-4 weeks before introducing them to the main display tank. Also, maintain good water quality and minimize stress levels in the tank.
  • Marine Velvet (Amyloodinium ocellatum): A highly contagious parasitic disease that appears as a fine gold or brown dust on the fish’s body. Prevention methods include quarantining new arrivals, maintaining proper water quality, and using a UV sterilizer to kill free-floating parasites.
  • Lateral Line Erosion (Head and Lateral Line Erosion – HLLE): This condition is characterized by pitting and erosion along the fish’s lateral line and head. 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, poor appetite, and abnormal feces. To prevent internal parasites, quarantine new fish and feed them high-quality, parasite-free food.

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

Author Note: Regular water changes, testing water parameters, and monitoring fish behavior can help you detect any issues early, allowing for timely treatment and prevention of disease spread.

Food & Diet

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

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

Author Note: It is important to feed Gem Tangs in small amounts multiple times a day rather than a large meal once a day. This will help prevent bloating and ensure that the fish receive adequate nutrition. 

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

A Zebrasoma gemmatum looking for food

Behavior & Temperament

These beautiful aquatic creatures spend a lot of their time swimming since they are very active. They are not as aggressive as other types of Tangs but are best kept with a diverse population in their aquarium. They may get along fine with your other fish, but make sure not to put them in a tank 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 tankmates when setting up your aquarium.


Breeding Gem Tangs in captivity is not an easy task. For one thing, it is hard to tell the female from the male. Due to the poky spike on their back, handling them is also difficult. Another reason that breeding is hard is that the male and female “broadcast spawn” their eggs. It is not known how long they take to develop.

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

Author Note: Breeding a Gem Tang is not necessarily impossible, but most Tangs are wild-caught, which should give you a hint about the success rate of breeding.

Wrapping Up

Overall, caring for Gem Tangs requires commitment and attention to detail. With proper care, these beautiful fish can live long and healthy lives in your aquarium. If you are considering making the big investment to add the Gem Tang to your collection, we highly recommend researching and preparing in advance to ensure a successful and enjoyable experience for both you and your fish.

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

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