QUICK STATS

Care Level: Moderate to Advanced
Diet: Herbivore / Omnivore
Temperament: Peaceful to Semi-Aggressive
Reef-Safe: Yes
Venomous/Toxic: No
Approximate Purchase Size: 2-5"
Approximate Max Size: Around 10"
Recommended Tank Size: 180-300 Gallons or Larger

MUSTARD TANG

The Mustard Tang (Acanthurus guttatus), also known as the Whitespotted Surgeonfish, Spotted Surgeonfish, or Spotband Surgeonfish, is a distinctive surgeonfish known for its gray body, bright white spotting, pale vertical bands, and yellow accents on the fins and tail. It has a more rugged, natural reef look compared to some of the flashier tangs, which is polite code for “less neon, more serious fish person.”

Mustard Tangs are active grazers that spend much of the day cruising through the aquarium and picking at algae on rockwork. In the wild, they are often found in shallow, high-energy reef zones and rocky areas, which helps explain why they need strong water movement, oxygenation, and plenty of swimming space in captivity.

This species is considered reef-safe and should not bother corals or most invertebrates when well-fed. Like many Acanthurus tangs, it may become territorial toward other tangs, surgeonfish, or similarly shaped algae grazers, especially after it becomes established. So yes, reef-safe, but not necessarily “group therapy retreat” safe. It is still a tang, tragically.

Note: Image is a representation of what to expect. The fish you receive may vary slightly in size, color, markings, maturity, and overall appearance.

AQUARIUM REQUIREMENTS

AQUARIUM SIZE

A minimum tank size of 180 gallons or larger is recommended for a juvenile or smaller Mustard Tang, with 300 gallons or larger preferred for long-term adult care. This species can reach around 10 inches and needs substantial open swimming room.

Mustard Tangs are strong swimmers and should not be housed in cramped aquariums. A long tank footprint is especially important because this fish needs horizontal swimming space, not just a tall glass box pretending to be useful.

HABITAT RECOMMENDATIONS

Mustard Tangs do best in large, mature aquariums with open swimming space, stable rockwork, strong filtration, and plenty of grazing opportunities.

Aquascaping: Provide open swimming room along with stable rock structures for grazing, shelter, and territory. Avoid overly dense aquascapes that block long swimming paths.

Substrate: Sand, fine aragonite, crushed coral, or bare-bottom systems can all work. This species does not depend heavily on the substrate.

Rockwork: Live rock is strongly recommended. It provides grazing surfaces, shelter, territory, and biological filtration.

Tank Maturity: A mature aquarium is preferred, especially one with natural algae and biofilm growth. Mustard Tangs benefit from regular grazing opportunities throughout the day.

Tank Cover: A tight-fitting lid is recommended. Tangs are not the worst jumpers, but large startled fish can still make sudden, athletic mistakes, because apparently the ocean did not teach them ceilings.

WATER PARAMETERS

Mustard Tangs are generally hardy once established, but they still need clean, stable marine conditions. “Surgeonfish” does not mean “immune to water quality problems,” though apparently every aquarium hobbyist must learn that through either research or financial pain.

Temperature: 72-78°F
pH Level: 8.1-8.4
Salinity: 1.020-1.026 specific gravity
Ammonia, Nitrite, and Nitrate: Ammonia and nitrite should remain undetectable. Nitrate should be kept as low as reasonably possible, ideally below 20 ppm.
Water Flow: Moderate to strong water movement is ideal. Provide strong oxygenation, efficient filtration, and enough flow to move waste toward filtration while still allowing comfortable swimming space.

DIET

Mustard Tangs are primarily herbivorous grazers, though they will accept a variety of omnivore foods in the aquarium. A diet rich in marine algae is important for maintaining body weight, color, digestion, and immune health.

PRIMARY DIET

Frozen Food: Offer algae-rich frozen foods, mysis shrimp, enriched brine shrimp, marine blends, and other high-quality frozen foods. We at Summit City Coral prefer frozen foods such as LRS Herbivore Frenzy and PE Mysis.

Prepared Herbivore Foods: High-quality herbivore pellets, marine algae pellets, spirulina flakes, and omnivore blends can help provide balanced nutrition.

Algae-Based Foods: Nori, seaweed sheets, spirulina, algae wafers, herbivore blends, and marine algae foods should be offered regularly. Clip seaweed sheets to the glass or rockwork so the tang can graze naturally.

Natural Grazing: Established live rock with film algae and biofilm can help support natural feeding behavior. This should be viewed as supplemental, not the whole meal plan. A tang is not a free algae-control employee with a built-in tail knife.

FEEDING FREQUENCY

Feed small amounts 1-2 times per day, with algae-based foods offered frequently. Tangs do best when they can graze throughout the day, so regular access to seaweed or algae-based foods is strongly recommended.

COMPATIBILITY

Mustard Tangs are generally peaceful to semi-aggressive and can work well in large reef aquariums with appropriate tank mates. They may become territorial toward other tangs, especially other Acanthurus species or similarly shaped algae grazers.

COMMON TANK MATES

Fish: Clownfish, cardinalfish, wrasses, gobies, blennies, rabbitfish, foxfaces, dwarf angelfish, larger peaceful fish, and other community reef fish.

Avoid: Other tangs or surgeonfish in smaller aquariums unless the tank is large enough and introductions are carefully managed. Avoid overly aggressive fish that may constantly harass the tang, as well as very timid fish that may be outcompeted.

Other Tangs: Use caution when mixing with other tangs. Add tangs carefully, provide plenty of space, and avoid combining too many similarly shaped or closely related species in undersized systems.

Invertebrates: Usually safe with cleaner shrimp, hermit crabs, snails, urchins, and common cleanup crew animals.

Coral: Mustard Tangs are considered reef-safe and should not bother soft corals, LPS, SPS, zoanthids, mushrooms, clams, or anemones. Like many herbivores, underfed individuals may become more likely to investigate surfaces they should leave alone, because hunger remains an unreliable moral compass.

BEHAVIORAL NOTES

Temperament: Peaceful to semi-aggressive. Usually manageable in large aquariums, but may become territorial once established.

Algae Grazing: Strong grazer for filamentous algae, film algae, and softer algae growth. Still requires regular feeding and should not be used as the entire algae-control plan.

Reef Compatibility: Excellent for reef tanks. They generally ignore coral and invertebrates when properly fed.

Swimming Style: Active swimmer that needs long open swimming paths and should not be cramped into undersized aquariums.

Tang Scalpel: Like other surgeonfish, Mustard Tangs have a sharp scalpel-like spine near the tail used for defense. Use caution when catching, transferring, or working around the fish. It is not venomous, just equipped with a tiny biological box cutter, because fish apparently needed tools.

Territoriality: May show aggression toward other tangs or similarly shaped fish, especially after becoming established.

Coloration: Typically gray to darker gray with white spots, pale vertical banding, and yellow accents on the fins and tail. Color intensity may vary depending on stress, maturity, diet, and lighting.

Tank Size Reality: This is a large, active tang that should be planned around adult size and swimming behavior, not purchase size. Juvenile tangs are how the ocean tricks people into future aquarium upgrades.

Rarity: Mustard Tangs are less commonly available than many popular tangs, making them a standout option for large reef systems when properly housed.

Jumping: A tight-fitting lid is recommended. Large fish can still make sudden, athletic mistakes.

ACCLIMATION PROCESS

This acclimation method helps reduce stress by gradually introducing the fish to your aquarium’s temperature and water chemistry.

1. TURN OFF THE LIGHTS & ATO

Turn off aquarium lights to reduce stress. If you have an Auto Top Off system, switch it off before starting acclimation.

2. FLOAT THE BAG

Float the sealed bag in the aquarium for 15-20 minutes to allow the temperature in the bag to equalize with the tank.

3. OPEN BAG, ADD FISH TO CONTAINER

Carefully open the bag and transfer the fish and shipping water into a clean bucket or container.

4. ACCLIMATE USING TANK WATER

Add 1/4 cup of tank water to the container every 5 minutes for 40 minutes.

5. TRANSFER FISH TO AQUARIUM

Once acclimation is complete, gently transfer the fish into the aquarium using a net or specimen container. Use caution near the tail spine when handling tangs. Discard the shipping water. Do not pour shipping water into your aquarium.

6. REFILL THE AQUARIUM WITH SALTWATER

You may need to replace the saltwater removed during acclimation with fresh mixed saltwater.