Regal Blue Tang
Paracanthurus hepatus
Large, active reef fish needing serious swimming spaceAdvanced
- Lifespan
- 10-20+ years
- Size
- 25-30cm (10-12in)
- Social needs
- Best kept one per tank unless the system is very large
- Time
- High
- Cost
- High
- Diet
- Omnivore, marine-algae-heavy
Overview
What is this animal?
- The Regal Blue Tang is a large, active reef fish that grows far bigger and lives far longer than most buyers expect.
- Reaching up to 30cm, it is a fast, near-constant swimmer that quickly outgrows the small tanks it is often sold for.
- This is an advanced fish.
- It needs a large, mature reef system, stable water, and an experienced keeper prepared for a decades-long, expensive commitment.
- It is frequently sold to beginners who lack the space and equipment it requires.
Temperament
- Generally peaceful toward other species but territorial toward other tangs and its own kind, especially in cramped quarters.
- A single specimen per tank is safest unless the system is very large and well aquascaped.
- Newly added fish are often shy and may hide or wedge into rocks.
- With time and space they become bold, active centrepiece fish that need room to roam.
A good fit for
- Experienced reef keepers with large systems
- Hobbyists wanting a long-term centrepiece fish
- Keepers committed to quarantine protocols
- Those with the budget for a large setup
Common mistakes to avoid
- Sold small, but grows to 30cm and outgrows small tanks
- Prone to marine ich and velvet
- Buying without a large, mature reef ready
- Diet too low in algae causing HLLE
Enclosure
Minimum 1,100 litres (291 US gallons)
Must be housed alone. Best kept one per tank unless the system is very large
- Provide an established reef aquarium of at least 1100L (290 gallons) with a long open swimming area and live rock with caves it can dart into when stressed.
- It is reef-safe and benefits from strong flow and good oxygenation.
- Keep parameters stable: temperature 24-27C (75-81F), salinity 1.024-1.026, pH 8.1-8.4, ammonia and nitrite at zero, and nitrate low.
- A fully cycled, biologically mature tank is essential before introduction.
Supplies
Setup
- Tank, stand and sump
- Return pump and powerheads
- Protein skimmer
- Reef lighting
- Rock and sand
- Salt mix, refractometer and test kits
- Quarantine tank
Ongoing
- Dried marine algae (nori) sheets in bulk
- Magnetic or suction veg clip
- Algae or herbivore pellets
- Herbivore frozen food blend
- Frozen mysis shrimp (for the small protein share)
- Vitamin or HUFA soaking supplement
- Second clip so nori can be offered in two places
Safe substrate: Aragonite sand · Dry or cured live rock · Bare bottom
Care routine
Daily
- Check salinity, temperature and flow
- Clip on dried algae
- Feed
- Head-count and look everyone over
- Top up evaporation with fresh water
Weekly
- Service the skimmer and filter socksevery 3 days
- Check head, lateral line and flanks
- Clean the glass
- Test the water
Monthly
- Water changeevery 2 weeks
- Calibrate the refractometer
- Check salt, RO/DI and reagents
Less often
- Deep-clean pumps and powerheadsevery 3 months
- Replace RO/DI filter mediaevery 6 months
Vet: Quarterly review with an HLLE check — every 3 months
Top resources for more info
Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-09-19.
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Diet
- Tangs are grazers that need a diet rich in marine algae.
- Clip dried nori or seaweed sheets in the tank daily and offer good-quality marine flakes or pellets plus frozen mysis or brine for protein.
- Vegetable matter should form the bulk of the intake.
- Frequent grazing supports digestion and reduces aggression.
- A varied diet with added vitamins helps prevent head and lateral line erosion (HLLE), which is linked to poor nutrition and water quality in tangs.
Health
- Blue tangs are prone to marine ich (Cryptocaryon) and velvet, partly because of their thin scaling and sensitivity to stress.
- Quarantine every new fish and minimise stress during transport and acclimation.
- They tolerate copper-based treatment well, which is a useful tool in a hospital tank.
- Watch for white spots, scratching, rapid breathing, and faded colour.
- Head and lateral line erosion points to poor diet or water quality.
- Stable conditions and good nutrition are the best preventatives.
Is your enclosure big enough?
Is this urgent?
In a reef, stability matters more than any single target number. A parameter moving fast does more damage than a parameter sitting slightly off.
Go now
Today
Quarantine every new animal, including corals and inverts. It is the single practice that separates a reef that lasts from a reef that restarts.
This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.
What it really costs
Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.
Bedding and substrate
In a marine system the rock and the sand are life support, and how you start them decides the first six months.
Safe
With a caveat
Never
This is our general list for saltwater fish. We have not built one specific to Tangs yet.
My kit says 0.25 ppm. Is that dangerous?
A liquid kit measures total ammonia, but only the un-ionised fraction is really toxic, and that fraction is governed by pH and temperature — each whole pH unit multiplies it roughly tenfold. So the same reading can be nearly harmless in one tank and lethal in another; this works out which one you are in.
Compare with other animals
The same axes for every animal, side by side — the way the guides are written makes that a fair comparison rather than two articles.
Tangs, side by side
Same axes, same care guides — the honest way to choose between types.
See all Tangs side by side →
