Longnose Butterflyfish Care: The Reef-Safe(ish) Yellow Beauty

Species Overview#

The Longnose Butterflyfish (Forcipiger flavissimus) is the species that finally makes butterflyfish realistic for the average reef keeper. Most members of the family Chaetodontidae are obligate coral or polyp eaters that starve in captivity, but the Longnose Butterflyfish picks tiny invertebrates from rockwork with a tweezer-like snout and accepts prepared foods within days of introduction. The body is solid lemon yellow, the face is split sharply between black above and silver below, and a single false eyespot sits on the rear of the anal fin to confuse predators.

These fish are active mid-water swimmers that patrol the entire length of the tank during daylight hours. Adults reach 8 to 9 inches across the Indo-Pacific, and a healthy specimen will live 5 to 7 years in captivity with stable water and a varied carnivore diet. They are not a beginner saltwater fish, but they are the most forgiving butterflyfish in the trade.

Adult size

8-9 in (20-23 cm)

Lifespan

5-7 years

Min tank

100 gallons

Temperament

Peaceful (territorial to own kind)

Difficulty

Intermediate

Diet

Carnivore

Identifying Forcipiger flavissimus vs. F. longirostris (The Big Longnose)#

Two species of Longnose Butterflyfish appear in the trade and they are constantly mislabeled. Forcipiger flavissimus is the common Yellow Longnose. Forcipiger longirostris, the Big Longnose or Forceps Butterflyfish, is rarer and sells for two to three times the price.

The visible difference is the snout-to-mouth ratio. F. flavissimus has a moderate snout with a clearly visible mouth opening at the tip. F. longirostris has a much longer, needle-thin snout and an almost invisible pinhole mouth. Count the dorsal spines if the snout length is ambiguous: flavissimus has 12 to 13 dorsal spines, while longirostris has 10 to 11.

This identification matters in practice. F. longirostris eats almost exclusively tube-foot tissue from sea urchins and benthic worms in the wild, making it notoriously hard to convert to prepared foods. If a store labels a fish "Longnose Butterflyfish" and is selling it for $80 or less, it is almost certainly F. flavissimus — the more affordable and more aquarium-friendly species.

Natural Habitat: Indo-Pacific Coral Reefs#

F. flavissimus has the widest range of any butterflyfish in the world, spanning the Red Sea, the entire Indo-Pacific, Hawaii, and across to the eastern Pacific coast of Mexico and Costa Rica. They occupy outer reef slopes, lagoons, and clear-water coral reefs from 5 to 130 feet deep.

In the wild, they pick small benthic invertebrates — polychaete worm tentacles, tube-feet from sea urchins, small crustaceans, and fish eggs — out of cracks in the reef structure. The long snout is purpose-built for reaching into crevices that wider-mouthed fish cannot access. This same behavior translates to the home aquarium: they will spend most of the day grazing live rock for copepods, amphipods, and any leftover food trapped in the rockwork.

Maximum Size and Lifespan in Captivity#

Adult Longnose Butterflyfish reach 8 to 9 inches in the wild and typically top out at 7 to 8 inches in a home aquarium. They are active swimmers with a tall, disc-shaped body that needs horizontal swimming distance more than vertical height. Captive lifespan runs 5 to 7 years with consistent feeding and stable water; some individuals have been documented past 10 years in mature systems.

Water Parameters & Tank Requirements#

Longnose Butterflyfish are tolerant within the standard reef range, but they have two real requirements that aquarists routinely underestimate: tank length and dissolved oxygen.

Minimum Tank Size (100+ Gallons for Swimming Space)#

A single Longnose Butterflyfish needs a 100-gallon tank with at least a 4-foot footprint. Smaller systems technically house the fish but cause chronic stress from lack of swimming room. The brief mentions 75 gallons as a floor for the species, and that figure works only in long, low aquariums (75-gallon "long" or 90-gallon footprints) — not in cube or hexagonal tanks.

For a pair, step up to 150 gallons with at least a 5-foot length. Two specimens in anything smaller will fight until one dies or stops eating. Mated pairs are sometimes available at specialty importers, and they are the only reliable way to keep two Longnose Butterflyfish in the same system.

Specific Gravity (1.020-1.025) and Temperature (72-78°F)#

Aim for the middle of each range. Hold temperature at 76°F and SG at 1.024 for the most consistent results. Butterflyfish in general are sensitive to swings — a 4-degree temperature change inside a single day will trigger ich outbreaks faster than in hardier species. Use a heater controller, not a single inline heater, to prevent thermal runaway.

Cycle the tank fully — ammonia and nitrite at zero for at least a full week — before introducing the fish. A Longnose Butterflyfish in an uncycled tank will refuse food and decline within days.

High Oxygenation and Flow Requirements#

This species comes from open reef slopes with steady current and high dissolved oxygen. A protein skimmer rated above your tank volume is a strong recommendation, both for water quality and for the surface agitation that drives gas exchange.

Aim for 15 to 20 times tank turnover in flow, with the powerheads angled to create broad horizontal current rather than localized blast zones. Longnose Butterflyfish swim continuously throughout the day, and they will fight a chaotic flow pattern; a clean lengthwise current along the tank lets them cruise without exhaustion.

Diet & Feeding#

Diet is where most Longnose Butterflyfish are won or lost. The first two weeks in a new tank determine whether the fish thrives or starves.

The "Longnose" Advantage: Reaching Into Crevices#

The pincer-like snout is the species' defining adaptation. In the aquarium, this means the fish will pull copepods, amphipods, and fish eggs out of rockwork that no other tank inhabitant can access. A mature reef tank with a thriving pod population is the ideal supplemental feeding ground for a Longnose Butterflyfish — they will graze constantly between scheduled meals.

This is also why the species transitions to prepared foods more easily than other butterflyfish: they are already evolved to pick small, mobile prey one bite at a time, which matches the way frozen mysis or chopped silverside disperses in an aquarium.

Overcoming Initial Feeding Shyness (Mysis, Brine, Clams)#

A new Longnose Butterflyfish often refuses food for the first 2 to 5 days. This is normal stress behavior, not failure. The proven sequence:

• Day 1-2: Lights off or dim. Do not attempt to feed. Let the fish settle.
• Day 3: Offer fresh clam on the half shell, wedged into a rock crevice. The smell and natural texture trigger the feeding response in 70% of new specimens.
• Day 4-5: Add live brine shrimp to the water column. Most Longnose Butterflyfish will hit live brine when they ignore everything else.
• Day 6+: Transition to frozen mysis shrimp, frozen Hikari Marine Cuisine, and high-quality marine pellets.

If the fish refuses everything past day 7, escalate to live blackworms or live mysis from a pod culture. Keep tank mates calm during feeding — aggressive eaters like damselfish or large angels will intimidate a new butterflyfish into refusing meals.

Frequency: Small Feedings 3x Daily#

Longnose Butterflyfish have small stomachs and high metabolisms. Three small feedings spread across the day work better than one or two large feedings. A working schedule:

• Morning: Frozen mysis or enriched brine shrimp
• Midday: Marine pellets (New Life Spectrum, TDO Chroma Boost)
• Evening: Chopped clam, krill, or frozen Hikari Marine Cuisine

Vary the menu weekly. A Longnose Butterflyfish on a single food type will lose color and condition over 3 to 6 months. Soak frozen foods in a vitamin supplement (Selcon, Vita-Chem) twice per week for color retention.

Tank Mates & Compatibility#

Longnose Butterflyfish are peaceful with most reef community fish but territorial against their own species and visually similar yellow fish.

Are They Reef Safe? (Caution with LPS and Feather Dusters)#

The honest answer is "reef safe with caution." Test results from long-term reef keepers:

• Safe: SPS corals (Acropora, Montipora, etc.), zoanthids, mushrooms, gorgonians, leather corals
• Usually safe: Most LPS — torch, hammer, frogspawn, candy cane, brain corals — in well-fed tanks
• At risk: Fleshy LPS like elegance corals, open brains in low-fed tanks
• Will eat: Feather dusters, Christmas tree worms, tube anemones, fan worms, fish eggs
• May nip: Tridacnid clam mantles, anemones (especially BTAs and carpet anemones) when underfed

The fish's behavior is highly individual. Some Longnose Butterflyfish ignore everything but their pellets for years. Others develop a taste for soft coral polyps after a single accidental nip. Add the fish last after evaluating the value of your reef inhabitants.

Best Community Tank Mates (Tangs, Wrasses, Anthias)#

Reliable Longnose Butterflyfish tank mates:

• Tangs (yellow, kole, tomini, hippo) — different niche, peaceful, reef-safe
• Wrasses (six-line, melanurus, fairy wrasses) — peaceful, mid-water swimmers
• Anthias (lyretail, dispar, bartlett's) — schooling, peaceful, similar dietary needs
• Royal gramma — peaceful, cave-dweller, no overlap in territory
• Clownfish — captive-bred Ocellaris or Percula; same temperament class
• Cardinalfish, firefish, gobies, blennies — all compatible with the Longnose

Avoiding Aggressive Butterflyfish and Large Angels#

Avoid in any tank under 180 gallons: other butterflyfish species (especially Auriga and Raccoon Butterflyfish), large angelfish (French, Queen, Emperor), triggerfish, lionfish, and any predator that views an 8-inch fish as food. Damselfish in small tanks will harass a new Longnose Butterflyfish into refusing food — remove established damsels before introducing the butterflyfish.

For an overview of compatible reef species, see the saltwater fish guide and the broader saltwater aquarium setup walkthrough.

Common Health Issues#

Longnose Butterflyfish are hardier than most members of the family, but they are still sensitive to two things that kill more forgiving fish: copper and ich.

Sensitivity to Copper-Based Medications#

Butterflyfish in general tolerate copper poorly. The Longnose is on the more tolerant end of the family, but a full therapeutic copper dose (2.0 to 2.5 ppm) will stress the fish and may damage the lateral line system permanently. Treat with copper only when necessary, and use a hyposalinity protocol (1.009 SG for 4 to 6 weeks) as a first-line alternative when treating ich in quarantine.

Tank Transfer Method (TTM) is the safest ich treatment for this species: move the fish to a new clean quarantine tank every 3 days for 12 days, completing four transfers total. This breaks the parasite life cycle without exposing the fish to copper.

External Parasites: Marine Ich and Velvet#

Marine ich (Cryptocaryon irritans) presents as small white spots on the body and fins, usually with flashing and increased respiration. Longnose Butterflyfish are particularly prone to ich during the first 30 days after collection. Quarantine every new specimen for 4 to 6 weeks before introducing to the display.

Marine velvet (Amyloodinium ocellatum) is faster and more lethal — fine gold-dust coating, rapid breathing, death within 48 to 72 hours if untreated. Move suspected velvet cases to quarantine the same day. The Longnose Butterflyfish handles low-level copper better than the True Percula clownfish but worse than most tangs; dose carefully.

Mouth Injuries During Transport and Acclimation#

The long, fragile snout is the species' weak point. Mouth damage during shipping is the #1 cause of mortality during the first week post-purchase. Damaged mouths cannot grip food, and the fish starves while staring at meals it cannot eat.

Inspect the snout at the LFS before buying. Look for redness, a curved or kinked snout, or a mouth that fails to close fully. A Longnose Butterflyfish with snout damage almost never recovers in a home tank — leave it at the store and wait for the next shipment.

Where to Buy & What to Look For#

Longnose Butterflyfish are available at most saltwater-focused fish stores. The challenge is sorting healthy specimens from shipping casualties — and especially from the species' notorious snout injuries.

Inspecting the Snout for Redness or Damage#

Watch the tank for at least 5 minutes before buying. A healthy Longnose Butterflyfish should be alert, swimming at mid-water, and probing rockwork with the snout. Red flags:

• Curved, bent, or asymmetric snout — almost certainly transit damage
• Redness or inflammation at the base of the snout — bacterial infection from injury
• Mouth that fails to fully close — the fish cannot grip food
• Faded yellow body — chronic stress or starvation
• Hollow belly behind the gill plate — starvation, internal parasites, or both
• Clamped fins, hiding behavior, or refusing to swim mid-water

The "Feeding Test" at Your Local Fish Store (LFS)#

The single most important purchase test for this species is a live feeding demonstration. Ask the store to feed the fish in front of you. A healthy Longnose Butterflyfish will:

• Strike at frozen mysis or pellets within 30 seconds of food entering the water
• Use the snout to pick food cleanly off rockwork
• Continue feeding until the food source is exhausted

A fish that refuses the feeding test is either too newly arrived (less than 7 days at the LFS), suffering from snout damage, or carrying a subclinical disease. Walk away. A good store will hold the fish for you and let you return in a week to retest.

Acclimation#

Use slow drip acclimation for Longnose Butterflyfish. Drip the bag water with display tank water at 2 to 3 drops per second for 90 to 120 minutes, then net the fish into quarantine (do not pour bag water in). Lights off for the first 48 hours. Expect the fish to spend the first 2 to 5 days hiding before it starts cruising the tank — this is normal, not a problem. Quarantine for a full 4 to 6 weeks before introducing to the display.

For a complete walkthrough on saltwater acclimation technique, see the saltwater aquarium guide.

Quick-Reference Cheat Sheet#