Mustard Guttatus Tang saltwater fish care guide

The Mustard Guttatus Tang, Acanthurus guttatus, is also sold as the Whitespotted, Spotband, or Spotted Surgeonfish. The body is disc-shaped and strongly compressed laterally, colored dark brownish-grey to silver-grey, and crossed by two or three vertical white bars near the head and midsection. Dense white spotting covers the rear half of the body, and the pelvic fins carry a vivid mustard-yellow that gives the fish its trade name. Adults reach roughly 10 inches. The species is distributed across the tropical Indo-Pacific, from Mauritius and Reunion east to Hawaii and Easter Island, north to southern Japan and south to Australia, where it occupies shallow, high-energy surge zones on seaward reefs generally shallower than about 25 feet.

Housing should reflect that surge-zone origin. Plan on a 125-gallon aquarium as a functional minimum for an adult, and understand that larger systems suit this fast, constantly moving swimmer better; specialist reef sources favor 180 gallons or more even for juveniles. Rockwork must be securely anchored to provide grazing surfaces without collapsing under heavy water movement, and the aquascape should leave long, uninterrupted lanes for swimming. Multiple powerheads and high turnover create the turbulent, chaotic flow this fish is built for, and a powerful protein skimmer paired with good aeration keeps oxygen levels high. Water quality should be pristine and stable in a mature system, and a UV sterilizer is a worthwhile addition for managing disease pressure in a tank holding a large, active surgeonfish.

Bright lighting suits both the fish and the algae growth it grazes. This is a moderate-care species rather than a beginner animal, largely because of its demand for space, flow, oxygenation, and consistent water conditions. Juveniles ship and acclimate considerably better than large adults, so starting with a smaller specimen improves the odds of a smooth transition.

In the wild, Acanthurus guttatus is a dedicated herbivore that grazes filamentous and calcareous algae from brightly lit, turbulent shallows. That grazing habit carries over completely in captivity, and a plant-based menu should form the core of its intake. Dried marine algae sheets offered on a clip, spirulina and kelp flakes, and prepared herbivore formulas all work well. Frozen mysis and brine shrimp can be used as supplements once the fish is settled, but they should never replace the algae component. Soaking foods in vitamin C is a useful practice for a species with this level of disease sensitivity.

Feed daily, and ideally in several small offerings spread through the day, since natural grazing is nearly continuous. Leaving an algae sheet available between feedings mimics that pattern and helps keep a large tang occupied. New arrivals deserve close attention: treat for internal worms as part of the quarantine routine, and watch the body profile carefully. A healthy specimen holds a rounded, full outline, while a pinched belly or hollowed area behind the head signals that the fish is not taking in enough food and needs intervention.

Dried Marine Algae Sheets Spirulina Flakes Kelp Flakes Herbivore Preparations Frozen Mysis Shrimp Frozen Brine Shrimp
On the reef, this surgeonfish shoals in groups ranging from ten to well over a hundred individuals, using numbers for safety while grazing exposed surge zones. In home aquariums it is almost always kept singly, since successful schooling has only been documented in very large public displays. Expect a fish that is active from lights-on to lights-out, cruising the water column at speed and pausing to pick at rock surfaces. Temperament is semi-aggressive, with territorial displays directed primarily at other surgeonfish that compete for the same grazing space.

Aggression is most pronounced toward other Acanthurus and Zebrasoma species, so any multi-tang arrangement demands a very large system, careful stocking order, and enough rockwork to break up sightlines. Gobies, anthias, and clownfish make reliable companions and are generally ignored. This tang is reef safe and does not damage corals, clams, or other sessile invertebrates, which makes it a good fit for SPS-dominant displays with intense light and chaotic flow. Shrimp, crabs, and snails are not targeted, though the usual caution applies when housing any large, fast-moving tang alongside very small or delicate tankmates.

FAQ

Frequently Asked Questions

About the Mustard Guttatus Tang

  • How big of a tank does a Mustard Guttatus Tang need?
    Plan on 125 gallons as a working minimum for an adult, with larger volumes strongly preferred. Specialist reef sources recommend 180 gallons or more even for juveniles, since adults are fast, tireless swimmers.
  • Is the Mustard Guttatus Tang reef safe?
    Yes. It does not harm corals, clams, or other sessile invertebrates, which makes it well suited to reef systems offering bright light and strong, turbulent flow.
  • Can a Mustard Guttatus Tang be kept with other tangs?
    It will compete for grazing territory with other Acanthurus and Zebrasoma species and can turn territorial toward them. Mixing tangs should be attempted only in very large systems with broken sightlines and careful introductions.