Crosseyed cardinalfish
Fowleria aurita
Crosseyed cardinalfish exhibits a distinct orange-red body with large, reflective eyes and a prominent dorsal fin.
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About the Crosseyed cardinalfish
Think of this little cardinal as a night owl that hangs in the shadows by day and pops out at lights-off to snack. It stays small, has that quirky crossed-eye look, and like other cardinals the male mouthbroods the eggs, which is super cool to watch if you ever get a pair to spawn. Give it rockwork to hide in and it settles right in.
Also known as
Quick Facts
Size
9 cm
Temperament
Peaceful
Difficulty
Beginner
Min Tank Size
30 gallons
Lifespan
3-5 years
Origin
Indo-Pacific
Diet
Carnivore - mysis, enriched brine shrimp, finely chopped seafood, small pellets
Water Parameters
24-29°C
8-8.4
20-40 dGH
Need a heater for this species?
This species needs 24-29°C in a 30 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it a rock-heavy scape with caves and shaded overhangs; keep flow low-moderate with some calm pockets. A single does fine in 20 gal; go 30+ for a pair.
- Run 76-80 F, 1.024-1.026 SG, pH 8.1-8.4, and 8-11 dKH. Ammonia/nitrite 0 and nitrate under 20, and avoid swings with steady top-off and small water changes.
- Feed small meaty foods (mysis, enriched brine, copepods, finely chopped seafood) 2-3x daily, ideally at dusk when they perk up. They usually learn 0.5-1 mm pellets if you mix them with frozen for a week.
- Peaceful roommates only: gobies, blennies, firefish, pink-streak or possum wrasses, and chill clowns. Skip dottybacks, damsels, hawkfish, big wrasses, or anything that can mouth a 2-3 inch fish.
- Reef-safe, but they may pick off tiny shrimp. Sexy shrimp and freshly molted cleaners are at risk.
- Keep one or a bonded pair; groups can scrap unless added together with tons of cover. If two square up nonstop, separate them.
- Breeding is classic cardinalfish stuff: the male mouthbroods; a bulged lower jaw and skipped meals means he is holding. To raise fry, move him to a quiet tank near release and feed rotifers then newly hatched brine.
- Common hiccups: they come in skinny, shy, and light-shocked. Quarantine, hit worms with praziquantel if needed, use a lid, and keep lighting on the mellow side.
Compatibility
Good Tankmates
- Small gobies and blennies that keep to the rocks (neon, watchman, tailspot) - calm neighbors and not crazy at feeding time
- Firefish and other dartfish - same chill hovering style, just give everyone a few bolt-holes
- Fairy or flasher wrasses - active but polite, and they do not nip at fins
- Easygoing clowns like ocellaris or percula - fine if they have their own spot and are not the boss of a tiny tank
- Assessors and royal grammas - cave lurkers that ignore cardinals, thrive in dim rocky setups
- Mandarins and other dragonets - peaceful pod-hunters, zero interest in bothering a shy cardinal
Avoid
- Dottybacks and similar temperamental nano bullies - they will tailgate and nip a timid cardinalfish
- Territorial damselfish (domino, three-stripe, many chrysiptera) - chasey and food-aggressive
- Hawkfish - perch and pounce types that harass or swallow small cardinals
- Big-mouthed predators or bruisers like lionfish, groupers, large Thalassoma wrasses, and triggers
Where they come from
Crosseyed cardinalfish (Fowleria aurita) show up across the Indo-Pacific. Think sheltered coral reefs, rubble slopes, and shady ledges. By day they tuck into crevices. At dusk they drift out to pick tiny crustaceans from the water column. If you give them a few dark hidey spots, you are basically recreating their favorite hangouts.
Setting up their tank
They are small and peaceful, so you do not need a giant tank. A single fish does well in a mature 20-gallon. For a small group, start around 30-40 gallons so they can get away from each other.
- Aquascape: Piles of porous live rock with caves, overhangs, and shadowy pockets. Branching rock or dead coral skeletons make great cover.
- Lighting: Keep it on the dimmer side or add shaded zones. Bright, bare tanks make them skittish.
- Flow: Moderate with calmer eddies behind rock. They like to hover, not fight a firehose.
- Lid: Tight-fitting. They are not serial jumpers, but a midnight spook can send any cardinal up and out.
- Mature system: Stable, cycled tank. They dislike ammonia spikes.
- Temp: 75-79 F (24-26 C)
- Salinity: 1.024-1.026
- pH: 8.1-8.4
- Ammonia/Nitrite: 0
- Nitrate: under 20 ppm
Acclimate slowly with lights off. A 30-45 minute drip acclimation keeps them from clamping up and refusing food later.
They are reef safe. They will not bother corals or inverts, but a big, hungry predator will absolutely bother them.
What to feed them
They go for small, meaty foods. Many new arrivals only wake up to eat after lights out, so plan for at least one twilight feeding at first.
- Frozen mysis and enriched brine shrimp (good starter foods)
- Calanus, copepods, or small plankton mixes
- Finely chopped shrimp, clam, or fish
- High-quality micro pellets once they recognize them as food
Feed 2 small meals a day. I like one just before lights out and a tiny top-up 30-60 minutes later. If they ignore pellets, mix a few into thawed mysis and let them chase the scent.
Use a red flashlight at night. They act naturally under red light and will come out to eat without spooking.
Soak foods in a vitamin supplement a couple times a week. It helps new fish bounce back from shipping and encourages appetite.
How they behave and who they get along with
Crosseyed cardinals are calm, hover-y fish that stick close to cover. Mine spent days tucked under a ledge and then floated out at dusk like a tiny blimp. They are not fighters, but they will posture with their own kind if space is tight.
- Keep one, a bonded pair, or a small group in a roomy, cave-filled tank. Watch for bullying and be ready to break line of sight with more rock.
- Good tankmates: small gobies, blennies, firefish, pipefish, peaceful wrasses like possum or pink-streaked, other small cardinals, cleaner shrimp.
- Skip: dottybacks, large or rowdy wrasses, triggers, groupers, lionfish, or anything that can fit a cardinal in its mouth.
- They are crepuscular-nocturnal. Give them dusk time to eat before the daytime crowd hogs everything.
Breeding tips
Like many cardinalfish, they are paternal mouthbrooders. If you see one fish holding a clump of eggs and refusing food, that is the male doing dad duty.
- Start with a relaxed pair or a small group and let a pair form. Lots of cover helps.
- Spawns usually happen at dusk. The male holds eggs for 1-2 weeks and often stops eating.
- If you want to try raising them, move the brooding male to a quiet nursery tank late in the holding period so he does not swallow the clutch during netting stress.
- Larvae are tiny and free-swimming. Think rotifers and copepods in greenwater, gentle circular flow, and spotless water. It is a project, not a weekend experiment.
You can also let nature run its course in the display. Some larvae may make it into the rockwork at night, but survival is usually low without dedicated rearing foods.
Common problems to watch for
- Goes off food: Often stress or too-bright lights. Dim the tank, add a cave, and offer small frozen foods at dusk.
- Harassment: Boisterous tankmates make them hide and starve. Rehome the bully or add more cover.
- Parasites (ich/velvet): Quarantine new fish. Cardinals can be sensitive to harsh treatments; follow measured dosing and keep oxygen high.
- Mouth injuries: They hover close to sharp rock. Avoid sudden netting and rough scaping.
- Jumping during spooks: Use a lid and avoid late-night slam-shut cabinet doors.
- Nitrate creep: They handle low nutrients best. Regular water changes and light feeding keep them happy.
If a new fish just stares at food, try turning off flow for a couple minutes and target-feed near its cave. Once it gets that first bite, the rest gets easier.
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