Weed cardinalfish
Foa brachygramma
The Weed cardinalfish features a dark brown body with distinctive vertical black stripes and bright red-orange eyes, reaching up to 10 cm in length.
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About the Weed cardinalfish
A tiny Hawaiian cardinalfish that disappears among seagrass and algae with its mottled, weedy camouflage. Males mouthbrood the eggs, so if you ever spot a pair, you might see dad carrying a clutch under his chin.
Also known as
Quick Facts
Size
6.4 cm
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
40 gallons
Lifespan
3-6 years
Origin
Central Pacific - Hawaiian Islands
Diet
Carnivore - zooplankton and small crustaceans; will take mysis, brine shrimp, copepods and other meaty frozen foods
Water Parameters
23-29°C
8.1-8.4
Need a heater for this species?
This species needs 23-29°C in a 40 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give Weed cardinalfish a 40-gallon or larger marine tank with lots of weedy cover; they feel at home tucked into macroalgae, seagrass, or fine-branching rock.
- Hold temperature at 23-29 C and pH at 8.1-8.4, and keep conditions steady rather than swinging around.
- Feed small, meaty foods that drift in the water column: mysis, enriched brine shrimp, copepods, and similar frozen fare sized for a tiny mouth.
- They are peaceful and small, so choose gentle tankmates and skip aggressive feeders or anything big enough to view them as a snack.
- Expect shy, cryptic behavior; provide multiple hiding spots and shaded nooks so they can disappear when they want.
- Males mouthbrood the eggs; if you see a male holding under his chin, give him quiet cover and minimal disturbance, though rearing the larvae at home is challenging.
- With solid husbandry they can reach about 3-6 years, so plan for steady feeding and regular maintenance over the long haul.
Compatibility
Good Tankmates
- Small, peaceful gobies (neon, clown, watchman) and shrimp-goby pairs that keep to the bottom and ignore quiet midwater fish
- Firefish and dartfish (Nemateleotris, Ptereleotris) with gentle temperaments and similar planktivorous feeding style
- Assessors and other small, shy basslets that stay near caves and do not chase timid tankmates
- Small, non-bullying blennies such as tailspot and fang blennies that graze and keep to the rockwork
- Peaceful fairy and flasher wrasses (Cirrhilabrus, Paracheilinus) that are active but not aggressive; provide cover so the cardinal can retreat
- Reef-safe inverts like cleaner shrimp (Lysmata), snails, small hermits, urchins, and serpent stars; avoid very tiny shrimps that could be prey
Avoid
- Predatory fish that may eat or harass small cardinals, such as hawkfish, lionfish/scorpionfish, groupers, large wrasses, and triggers
- Territorial damselfish and aggressive clownfish that bully shy, slow-feeding species
- Dottybacks (Pseudochromis) and very aggressive wrasses like sixline that harass and outcompete timid fish
- Very small ornamental shrimp and tiny crabs that may be viewed as food, especially freshly molted individuals
Weed cardinalfish (Foa brachygramma) is a tiny, peaceful Hawaiian species that vanishes among seagrass and algae thanks to its mottled, weedy camouflage. It stays small (up to about 6.4 cm), lives 3-6 years, and suits patient keepers with some marine experience.
Quick facts - Marine, Central Pacific (Hawaiian Islands) - Max size 6.4 cm - Minimum tank 40 US gallons - Peaceful - Intermediate care - Temperature 23-29 C - pH 8.1-8.4.
Origin and natural habitat
Native to the Hawaiian Islands in the Central Pacific, this fish keeps close to cover in weedy, algae-rich areas. The mottled pattern breaks up its outline so well that you may not see it until it moves. That same preference for dense, plant-like structure carries over to the aquarium.
Aquarium setup and water conditions
Give a single Weed cardinalfish a minimum of 40 gallons so it has space and quiet corners away from faster feeders. Build a scape with lots of nooks and shaded patches: branching rockwork, overhangs, and clumps of macroalgae or other weedy cover help it settle and show natural behavior. Keep stable marine conditions, with temperature 23-29 C and pH 8.1-8.4.
Provide weedy-looking cover. Clumps of macroalgae or fine, brushy structures make this species feel secure and bring out its camouflage.
Diet and feeding
A zooplanktivore that eats tiny crustaceans, it readily accepts meaty frozen foods of appropriate size: mysis, enriched brine shrimp, copepods, and similar items. Start with moving foods and deliver them near its hiding places with a pipette if needed. Small portions offered more than once per day suit this species better than a single large meal. Many individuals ignore dry foods at first.
Because this fish preys on small crustaceans, very tiny ornamental shrimp or their larvae may be at risk.
Behaviour and tankmates
Peaceful and shy, the Weed cardinalfish spends time tucked into cover and does poorly with boisterous or predatory tankmates that rush food. Pair it with other small, calm fishes so it is not outcompeted at feeding time. Dimmer areas and line-of-sight breaks help it feel comfortable and visible.
Males are mouthbrooders. If a pair forms, you may see the male holding a clutch of eggs under his chin.
Common problems and how to avoid them
- Reluctant feeding: Begin with frozen or live zooplankton-like foods and feed small amounts more than once daily.
- Outcompeted by faster fish: Choose gentle tankmates and target-feed near its refuge.
- Constant hiding: Add more dense cover and shaded areas to reduce stress.
- Parameter swings: This small cardinalfish does best with stable marine conditions within 23-29 C and pH 8.1-8.4.
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