Dottybacks · Pseudochromidae

Longfin Dottyback

Manonichthys polynemus

Dark gray body with neat horizontal rows of small yellow dots, yellow patch below eye and at pectoral base, elongated thread-like pelvic fin rays and dark translucent fins, gently rounded tail. A colorful cave-dwelling carnivore whose territorial behavior needs careful planning.

Care levelIntermediate

Prepared foods and hardy behavior do not remove its territorial risk. Introductions, shelter and monitoring make this an intermediate planning choice.

Recommendation

Would you recommend this fish for a suitable saltwater aquarium?

30+ galRecommended tank

5 inchesAdult size

Aggressive / territorialTemperament

Generally compatibleCoral safety

+ Why you’ll love them

Distinctive Longfin appearance.
Rockwork and sheltered crevices provide natural cover.
Suitable marine meaty foods can support a varied captive diet.

! Things to consider

Territorial behavior can put timid and similar-looking fish at risk.
Ornamental shrimp and small crustaceans are prey risks.
Other dottybacks may provoke disputes; gallons alone do not create separate territories.

Tank and habitat

Recommended volume: 30 US gallons or larger; allow for stocking and layout.
Full-grown size: 5 inches (maximum adult size)
Tank footprint and swimming space: Use a tank with substantial horizontal rockwork, multiple shaded caves and broken sight lines. Provide room for its larger adult body and robust tank mates. Group stocking may need much more room than the individual reference.
Tank maturity: Use a fully cycled, stable marine aquarium with established shelter and filtration. No dependable species-specific month threshold is established here; age alone does not prove readiness. Suggested tank age is a planning guide, not proof of readiness. Complete cycling, stable water and the right food supply are essential.
Habitat and equipment: Secure porous rockwork, shaded crevices, unobstructed feeding access and suitable flow. Cover escape openings and protect intakes. Retain several escape routes for less assertive inhabitants.

Care and compatibility

Temperament: Aggressive / territorial
Why this care level: Prepared foods and hardy behavior do not remove its territorial risk. Introductions, shelter and monitoring make this an intermediate planning choice.
Suitable tank mates and conflicts: Aggressive / territorial: small or timid gobies, firefish, basslets and other dottybacks are poor choices. Use larger, robust tank mates and separate territories; have a separation plan.
Alone, pair or group: One individual is the simpler plan. Do not assume a random pair, a large group or different dottyback species will coexist. Specialist breeding arrangements do not establish safety for arbitrary adults. Use a confirmed pair only with suitable expert guidance and separate if necessary.

Corals and invertebrates

Coral safety: Generally compatible
Generally compatible with coral tissue. Coral safety does not mean compatibility with all fish or invertebrates; monitor the individual.
Shrimp safety: Not compatible
Treat ornamental shrimp as potential prey. Small, newly introduced or molting shrimp are particularly vulnerable; feeding well does not eliminate predation.
Snail safety: With caution
Predation on small benthic invertebrates is possible. Monitor small snails and do not assume a cleanup crew is protected.
Clam safety: Generally compatible
Generally compatible with clam tissue. Observe individual behavior and ensure that clam requirements are met independently.

Food and feeding

Diet: Carnivore; varied marine meaty foods
Feeding plan: Offer appropriately sized, varied marine meaty meals in small portions multiple times daily. Match food size to the adult mouth without using live aquarium tank mates as feeders. Confirm actual intake and body condition.
Prepared or live food: Mysis, enriched brine shrimp and finely chopped suitable marine seafood; quality carnivore pellets or flakes if the individual accepts them. Obtain the seller’s established feeding routine.

Water conditions

Temperature: 72–78 °F (22–26 °C). Published supplier aquarium reference range. Maintain stability and consider every inhabitant.
Specific gravity: Specific gravity 1.020–1.025 is the tropical fish-care reference used here. Also meet the needs of corals and other invertebrates; avoid abrupt changes.
pH: pH 8.1–8.4. Keep conditions stable and monitor alkalinity rather than making abrupt corrections.

Long-term care

Lifespan: The sources used here do not establish a dependable typical captive lifespan for this entry. Plan for long-term care rather than an invented numerical average.
Growth and future planning: The supplier gives an approximate adult reference of 5 inches. Sex, age and locality may affect appearance; plan for adult space rather than purchase size.

Before you buy

Is this fish right for your tank?: The supplier lists 30 US gallons or larger as an individual aquarium reference. Aggressive / territorial: small or timid gobies, firefish, basslets and other dottybacks are poor choices. Use larger, robust tank mates and separate territories; have a separation plan.
Buying checklist: Confirm Manonichthys polynemus, observe feeding, inspect fins and breathing, and obtain origin and feeding details. Longfin Dottyback is listed as Manonichthys polynemus. Confirm the scientific name; similar trade names and colors are not reliable identification by themselves. Plan quarantine before introduction.

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