Regal tang
Paracanthurus hepatus
The regal tang is instantly recognisable by its bright blue colour and black palette-like marking. Paracanthurus hepatus nevertheless grows far larger than the tiny fish often offered for sale: plan for approximately 31 cm and a very active swimmer. It belongs in a large, long, biologically stable marine system. A promise to upgrade later is not a sound basis for purchase. The fish needs both open water and secure resting places, and can outcompete smaller, quieter residents at feeding time. Contrary to a simple “algae eater” label, natural-history accounts also describe zooplankton feeding. A varied marine ration containing animal and plant ingredients therefore makes more sense than only algae or only meat. This is a fish for a prepared keeper able to accommodate its adult size, diet and health over the long term, not a beginner’s small first reef.
Plan your aquarium →At a glance
- Adult size
- Approximately 31 cm
- Aquarium length
- At least 180 cm
- Minimum aquarium volume
- At least 700 L
- Temperature
- 24–26 °C
- Specific gravity (SG at 25 °C)
- 1.024–1.026 SG
- Salinity
- 32–35 ppt
- pH
- 8.1–8.3
- Difficulty
- Difficult
- Temperament
- May compete for food
- Diet
- Omnivore
- Swimming zone
- Middle
- Reef safety
- Generally reef safe
- Suitable for beginners
- No
- Social needs
- Solitary
- Keeping conspecifics
- Prefer one individual
Cautious husbandry guidance for adults, not a complete stocking calculation. Assess tank length, layout and the entire community together.
About this species
The yellow tail, blue background and black pattern distinguish it from the yellow tang and other fish locally called “blue tang”. Use Paracanthurus hepatus as the reliable identity when buying or researching it. Adults can reach approximately 31 cm. Sharp structures at the tail base require care when handling. Wedging into a crevice may be normal resting behaviour; sudden poor balance, laboured breathing or injuries are different and need investigation.
Natural habitat
The species comes from Indo-West Pacific reefs. Open water near shelter allows it to collect small food particles and retreat when threatened. This explains its need for long swimming routes alongside secure rock crevices. A solid wall of coral reduces useful space. Prefer open passages and resting sites sized for the adult body. Juveniles may use different refuges from adults, so ensure openings do not become dangerously narrow as the fish grows.
Aquarium and layout
For planning, allow at least approximately 700 L and 180 cm of length. Length is essential and cannot be replaced by extra height. Provide turning width and an uninterrupted swimming route. These figures are a cautious lower bound for a suitable simple community, not a maximum permissible stocking level. Extra tangs or large territorial neighbours require a larger-scale assessment. Gas exchange, filtration and controlled flow support activity but cannot repair a physical shortage of space.
Water conditions
Keep temperature, salinity and pH stable and inspect the complete installation when behaviour changes suddenly. A large active fish places demands on oxygen supply and waste processing. Measure ammonia/ammonium and nitrite after additions, maintenance problems or filtration failure, and track nitrate over time. Prepare replacement water beforehand and check temperature and salinity. Replace evaporation with suitable fresh water. A high fish load does not justify blind dosing: measure first and balance maintenance with stocking.
Behaviour and group size
A regal tang moves extensively and may displace smaller fish at meals. Even without overt aggression, its activity can stress a timid neighbour. Provide quieter feeding areas where food actually reaches calmer residents. Conflicts with other large active fish are possible, particularly where swimming routes narrow. Watch injuries, escape behaviour and repeated pursuit. A fish that remains among rocks should be assessed for intimidation or illness rather than automatically dismissed as naturally shy.
Feeding
Offer a varied marine ration. Appropriate animal foods reflect the documented plankton intake, while marine algae and suitable complete feeds supply plant components. Use small readily swallowed portions and monitor individual condition. A complete food must be demonstrably appropriate in its actual formulation; a generic name or high spirulina percentage is insufficient. Grazing surfaces are useful without replacing a controlled ration. Distribute feeding locations if faster fish claim the whole portion.
Reef safety
The species is generally kept as reef safe. This describes its usual risk of coral consumption, not whether a reef aquarium is large enough. An undersized reef remains unsuitable even with perfectly matching water values. Keep busy swimming lanes clear of fragile branching colonies. Individual behaviour and adequate feeding remain relevant. Lack of evidence for a particular invertebrate group is not automatically converted into a low-risk assessment.
Keeping with other fish
A yellow tang can only be considered in a suitably spacious system with enough grazing area, clear swimming routes and several resting places. Either species’ individual minimum is not automatic joint advice. Calm cardinalfish or small bottom-dwellers must be able to feed without continual displacement by activity. A shy firefish deserves extra caution. Beside a large triggerfish, bite risk and territorial behaviour add to the space requirements; overlapping seawater ranges say little about those problems.
Keeping with invertebrates
Larger reef invertebrates are not usual food targets, but this does not justify a guarantee covering every size and species. Small plankton-like animals can be eaten. Also assess the reverse direction: a large crab may injure a resting fish. Uncertainty remains visible for clams, worms and other categories lacking specific evidence. Protective layout can reduce risk but cannot substitute for an adequately documented choice of species.
Breeding
The early life stages require specialist care and food; this is not an ordinary home-reef breeding fish. Adult husbandry does not provide a complete recipe for raising pelagic larvae. No unsupported timings, counts or simple breeding-box method are given. Ask for traceable provenance if a fish is sold as captive-bred. The availability of cultured specimens must not be used to understate their eventual space requirements.
Possible problems
Monitor skin condition, possible parasites, breathing and nutrition. Colour alone is not a diagnosis. Check water quality and social stress, and seek specialist help for white spots, injuries or persistent feeding problems. Quarantine and treatment must fit the actual condition and product; universal fixed copper doses are unsafe. Do not treat an ill fish in a mixed reef without a plan. Adequate swimming room, quiet refuges and a varied ration remain the everyday foundation.
Keeping with other species
Ocellaris clownfish
Suitable with conditionsThe tang sets a much greater minimum length and needs clear swimming lanes. Give the smaller neighbour cover and a feeding area outside the busy route.
View species profile →
Royal gramma
Suitable with conditionsThe tang sets a much greater minimum length and needs clear swimming lanes. Give the smaller neighbour cover and a feeding area outside the busy route.
View species profile →
Banggai cardinalfish
Suitable with conditionsThe tang sets a much greater minimum length and needs clear swimming lanes. Give the smaller neighbour cover and a feeding area outside the busy route.
View species profile →
Pajama cardinalfish
Suitable with conditionsThe tang sets a much greater minimum length and needs clear swimming lanes. Give the smaller neighbour cover and a feeding area outside the busy route.
View species profile →Sources & review
This care guide draws on several specialist sources and was last checked on .