Bicolored foxface
Siganus uspi
The Bicolored foxface displays a striking yellow-orange body with a prominent black mask and robust, elongated dorsal fin.
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About the Bicolored foxface
Siganus uspi is that super sharp-looking Fiji rabbitfish with the hard two-tone split - dark front half, bright yellow rear half. It is an algae-grazer that tends to cruise calmly, but it has venomous fin spines, so you treat it with respect any time you are netting or working in the tank.
Also known as
Quick Facts
Size
24 cm
Temperament
Semi-aggressive
Difficulty
Intermediate
Min Tank Size
75 gallons
Lifespan
8-12 years
Origin
Western Pacific (Fiji)
Diet
Herbivore - macroalgae/nori, spirulina-based foods, herbivore pellets; will also take frozen foods occasionally
Water Parameters
24-28°C
8-8.4
8-12 dGH
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This species needs 24-28°C in a 75 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give a bicolored foxface room to cruise - I'd call 90+ gallons the starting point, with lots of rock to graze and a couple caves to wedge into when it spooks.
- Keep salinity stable around 1.025-1.026 and temp 76-79F; they get cranky fast if you let pH swing (shoot for 8.1-8.4) or if nitrates creep high.
- Feed like its a grazer: nori on a clip most days, plus spirulina flakes/pellets and a little mysis or brine as a treat - they stay way less bitey when they're not hungry.
- They usually behave with other chill community fish, but skip tankmates that love to nip fins or harass (some damsels, dottybacks, and pushy angels can make it hide nonstop).
- Reef note: a well-fed one can be great for algae, but a hungry foxface may sample soft corals or some LPS - keep nori available and don't let it run out of greens.
- Watch the dorsal spines - they are venomous; use a container, not a net, and be careful when it 'plays dead' and wedges into rock.
- Quarantine if you can: they can pick up marine ich, and stress shows up as blotchy color and refusal to eat - once they settle, they are usually pigs at feeding time.
Compatibility
Good Tankmates
- Fairy and flasher wrasses (Cirrhilabrus and Paracheilinus) - they are quick, not too pushy, and they stay out in the water column so the foxface usually ignores them
- Clownfish pairs (Ocellaris or Percula) - they mostly mind their own business around their corner/anemone, and a bicolored foxface is usually chill with them in a normal sized reef
- Peaceful reef gobies and blennies (watchman goby, tailspot blenny, lawnmower blenny) - different niche, they perch and graze, and the foxface is more of a cruise-and-nibble type
- Tangs of similar temperament in a big enough tank (yellow tang, kole tang) - generally works if everyone has swimming room and you add the foxface and tangs with some planning, because they are all grazy types but not usually murdery
- Reef-safe-ish angels that are not total jerks (coral beauty, flame angel) - in my experience they can coexist fine as long as neither one is the established bully and there are plenty of rocks to break up sight lines
- Most non-aggressive basslets (royal gramma) - they claim a cave and do their own thing, and the foxface usually just cruises past without drama
Avoid
- Other rabbitfish or foxfaces (including another Siganus) - this is where people get burned, they often turn into turf wars unless you have a very large tank and add them carefully at the same time
- Nippy semi-aggressive stuff that likes to harass slower fish (some damsels, dottybacks) - they will pick at the foxface, and the foxface will get stressed and go spine-first if it feels cornered
- Big aggressive triggers and puffers - they can nip fins, pick at the foxface, and a rabbitfish is not the kind of fish you want in a bitey tank
- Territorial large wrasses and bruisers (some Thalassoma wrasses, big hawkfish types) - they can be too in-your-face, and the foxface does best with tank mates that do not constantly body-check it
Where they come from
The bicolored foxface (Siganus uspi) is a rabbitfish from Fiji and nearby island areas. They hang around lagoons and reef slopes where there is lots of algae and rubble to pick at. That background explains most of their personality in a tank: always grazing, always curious, and usually pretty chill.
Setting up their tank
Give this fish room to cruise and a lot of rockwork to graze. Foxfaces are active swimmers, but they also like to wedge themselves into rock to sleep (sometimes they pick a weird corner and go pale at night - totally normal).
- Tank size: I would not do one in less than 90 gallons, and 120+ is even nicer once it hits adult size
- Aquascape: open swim lanes plus a big rock pile with caves/overhangs
- Flow: moderate to strong is fine, as long as there are calmer pockets to rest
- Lighting: whatever your reef runs - they will graze more under brighter light because algae grows faster
- Cover: lid or mesh top is smart; they can spook-jump
Foxfaces have venomous dorsal spines. It is not usually a hospital trip, but it hurts a lot. Use a container to move them, not a net, and watch your hands when they pin themselves into rock.
Stability matters more than chasing numbers. Aim for normal reef salinity and keep ammonia and nitrite at zero. They handle routine reef parameters well, but they do not love sudden swings - especially after shipping.
What to feed them
Think of them as an algae grazer that still wants real meals. If you just feed meaty food, they can get skinny over time even if they look busy all day. The best results I have had were with constant greens plus a couple of mixed feedings.
- Daily greens: nori/seaweed sheets on a clip (I like to offer a small piece twice a day rather than one huge sheet)
- Prepared foods: spirulina flakes/pellets and quality herbivore pellets
- Frozen: mysis, brine, and mixed reef blends a few times a week
- Fresh options: blanched romaine or spinach in a pinch (not as good as marine algae, but it can help a picky new fish start eating)
If your foxface ignores the algae clip at first, rubber-band a strip of nori to a small rock and place it near where the fish likes to hide. They seem to trust it more when it looks like something growing on the reef.
They will absolutely help with nuisance algae, but do not buy one expecting it to mow down everything overnight. If the tank is too clean, you need to provide greens or they get that pinched-in look behind the head.
How they behave and who they get along with
Most bicolored foxfaces are peaceful and a little shy at first. After a week or two they usually turn into a bold grazer that follows you around. They can change color fast when stressed or sleeping, so a sudden pale pattern is not automatically a disaster.
- Good tankmates: clownfish, wrasses, gobies, blennies, cardinals, most reef-safe angels, tangs in larger tanks
- Use caution with: other rabbitfish (can fight in smaller systems), very aggressive damsels, big triggers, and pushy established tangs
- Reef compatibility: generally reef-safe with corals, but a hungry foxface may nip some softies and LPS (zoas, fleshy brains, and some leathers are the usual complaints)
If you see occasional coral nipping, try adding more algae feedings first. In my tanks, coral sampling usually showed up when the fish ran out of easy greens.
They are not usually bullies, but they will defend their personal space with those spines if a fish keeps crowding them. Give them a cave or two they can claim and you will see fewer standoffs.
Breeding tips
Breeding Siganus uspi at home is not something most hobbyists pull off. In the wild they spawn in groups and the larvae are pelagic and tricky to raise. If you ever see two adults doing a dusk-time rise and release behavior, that is about as far as it tends to go in a typical home reef.
If you want to try anyway, your best shot is a large system with multiple rabbitfish and very consistent day-night lighting. Even then, raising the larvae is the hard part, not getting eggs.
Common problems to watch for
Most issues I have seen with foxfaces come from shipping stress, not enough greens, or tankmates that never let them relax. They are hardy once settled, but the first couple of weeks can be bumpy.
- Ich/velvet after purchase: common in rabbitfish like many marine fish, so quarantine and observation helps a lot
- Refusing food: usually a new-tank jitters thing - offer nori near their hiding spot and keep the lights a bit lower for the first day or two
- Weight loss: add more algae-based foods and feed smaller portions more often
- Coral nipping: often tied to hunger or a too-clean tank with no algae film
- Fin tears and scrapes: they wedge into rock and can get roughed up if the aquascape has sharp points
- Spine stings: happens during capture/transfer - plan your moves and do not rush
If you get stuck by a spine, hot (not scalding) water soaks usually help with pain because the venom is heat-labile. Seek medical help if you have severe swelling, breathing issues, or the pain is not settling down.
One last practical thing: watch for the fish wedging itself somewhere you cannot reach. They love tight sleeping spots, and if a rock shifts, it can pin them. Stable rockwork is not just for corals - it can save your foxface too.
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