Narrow Lined Pufferfish

The Narrow-Lined Pufferfish, Arothron manilensis, is a distinctive saltwater fish recognized by the fine, flowing horizontal lines that run across its pale gray, tan, or greenish body. A dark patch surrounding the base of the pectoral fin adds contrast to its subtle patterning, while its expressive eyes, rounded profile, and characteristic pufferfish swimming style give it tremendous personality in the marine aquarium.

Native to the Western Pacific, this species inhabits sheltered reef flats, lagoons, estuaries, seagrass beds, and sandy or silty coastal habitats. Juveniles may also occur around mangrove environments. Rather than being restricted to exposed coral reefs, the Narrow-Lined Pufferfish naturally favors relatively protected shallow-water habitats where it searches the bottom for small invertebrates and other food.

Reaching approximately 12 inches as an adult, this is a substantial marine aquarium fish best suited to a spacious fish-only or fish-only-with-live-rock aquarium. Its intelligence, unusual appearance, and interactive feeding behavior make it an excellent centerpiece for aquarists prepared for its predatory diet and lack of reef compatibility.

Quick Care Guide

Care Level: Moderate
Minimum Tank Size: 125 gallons
Adult Size: Up to 12.2 inches (31 cm)
Temperament: Semi-Aggressive
Diet: Carnivore
Reef Safe: No
Region: Western Pacific, from Southeast Asia and the Philippines through northern Australia and eastward to Samoa and Tonga, north to southern Japan
Scientific Name: Arothron manilensis

Tank Requirements

Provide a spacious aquarium with a combination of open swimming room and sturdy rockwork that creates caves, overhangs, and sheltered resting areas. The aquascape should be secure, as an adult puffer is a powerful, heavy-bodied fish capable of disturbing loosely positioned decorations.

A sand substrate works particularly well and complements the species' natural association with sandy, silty, and seagrass environments. Moderate water movement is generally sufficient, but excellent filtration, oxygenation, and consistent water quality are important because puffers are enthusiastic feeders that can create a significant amount of waste.

Choose tankmates and aquascaping with the fish's adult size in mind. A secure lid is recommended, and the aquarium should provide enough open space for comfortable turning and cruising.

The adult minimum is 125 gallons. Evaluate the usable footprint as well as the gallon rating: the fish must be able to turn, reach a resting place, and pass companions without repeated close contact.

Leave access around the base of the aquascape for removing food fragments. Support heavy rocks securely before adding loose substrate, and retain more than one route between shelter and open water.

Diet and Feeding

The Narrow-Lined Pufferfish is a carnivore that naturally feeds on benthic invertebrates, including mollusks and crustaceans. In captivity, offer a varied diet of meaty marine foods such as chopped shrimp, clam, mussel, squid, crab, krill, mysis shrimp, and quality frozen carnivore preparations.

Hard-shelled foods are especially important. Like other puffers, this species has continuously growing dental plates, and regularly feeding appropriate shell-on foods helps provide natural wear.

Feed appropriately sized portions once or twice daily, adjusting the amount according to the fish's condition and the aquarium's nutrient load. Avoid relying exclusively on soft foods, which do little to help maintain the teeth.

Use a rotation of accepted foods rather than one item as the entire diet. Practical options include:

• Mysis shrimp and enriched brine shrimp

• Chopped marine shrimp

• Clam or mussel meat

• Appropriately sized pieces of squid

• Quality frozen marine carnivore preparations

• Suitable marine pellets when accepted

Observe food intake and body condition instead of using eagerness to eat as the only guide to portion size. Remove leftover pieces promptly, including those carried into shelters.

Use suitable feeding tools and keep fingers away from the mouth. Investigate a persistent change in appetite or difficulty handling food rather than repeatedly increasing the ration.

Temperament and Tankmates

Although often personable toward its keeper, the Narrow-Lined Pufferfish should be considered semi-aggressive and predatory. Individual temperament can vary, and adults may nip the fins of slower or more passive fish.

Suitable tankmates generally include robust medium to large marine fish capable of defending themselves without being excessively aggressive. Avoid very small fish, delicate long-finned species, and slow-moving tankmates that may be viewed as prey or targets for exploratory biting.

Keeping one Narrow-Lined Pufferfish per aquarium is the safest approach. Mixing puffers or other similarly shaped territorial species should be reserved for exceptionally spacious systems with careful observation.

Compatibility must be reassessed after the fish settles in and as it matures. Repeated chasing, damaged fins, missed meals, or a fish confined to one corner are signs that the arrangement is not working.

Have a practical separation plan before introductions. Visual barriers and distributed feeding can reduce some competition, but they cannot make a persistently aggressive combination safe.

Reef Compatibility

The Narrow-Lined Pufferfish is not reef safe. Its natural feeding behavior makes ornamental invertebrates vulnerable, including shrimp, crabs, snails, clams, and other mollusks.

Corals and other sessile organisms may also be bitten or damaged as the fish explores and searches for food. For this reason, the species is best maintained in a fish-only or fish-only-with-live-rock aquarium rather than a traditional reef aquarium.

Regular feeding does not guarantee that potential prey will be ignored. Select the display around the animals you need to protect rather than assuming that an established cleanup crew is safe.

Secure loose coral fragments or decorations and preserve clear routes around the aquascape. A short period without damage is not proof of permanent compatibility.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Maintain an established biological filter and good oxygenation. Ammonia and nitrite should remain undetectable, and routine testing should guide water changes and nutrient export rather than waiting for visible deterioration.

Check salinity with a calibrated instrument and replace evaporated water with freshwater. Match replacement saltwater to the aquarium during water changes, and avoid sudden changes in temperature, salinity, or pH.

Keep feeding and maintenance consistent. Changes in appetite, breathing, or normal activity warrant investigation even when the water looks clear.

Common Considerations

• Adult Size: Reaches approximately 12 inches and develops into a substantial, heavy-bodied fish requiring significant swimming and turning space.

• Predatory Feeding: Ornamental shrimp, crabs, snails, clams, and other invertebrates should be considered potential food.

• Dental Maintenance: Regular hard-shelled foods are important for naturally wearing down the continuously growing dental plates.

• Tankmate Selection: Avoid small, delicate, or long-finned fish that may be eaten, harassed, or nipped.

• Handling: Puffers should be transferred carefully and should never be intentionally encouraged to inflate, as inflation is a stress response.