Pacific Redfin Butterflyfish

Chaetodon lunulatus

Saltwater Fish Species Group: Butterflyfish Family: Butterflyfish

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Water parameters

Temp 76-80 F Temperature

Maintaining a stable and appropriate temperature is critical for the survival of aquatic life.

pH 7.8 - 8.4 potential of Hydrogen

Measuring the acidity or alkalinity of water on a 0–14 scale, where 7 is neutral, 7 is alkaline.

NO3 1-20 ppm Nitrate

While less toxic than ammonia, high nitrate levels (above 40–80 ppm) are important to monitor because they can cause fish stress, stunted growth, and harmful algae blooms.

NO2 <0.0001 ppm Nitrite

It is a highly toxic, intermediate compound in the nitrogen cycle produced from broken-down ammonia

PO4 0.01 - 0.1 ppm Phosphate

It is essential for plant development but must be managed, as excess levels trigger nuisance algae blooms and inhibit coral calcification.

NH3 <0.1 ppm Ammonia

It is the primary killer of aquarium fish, causing gill damage, stress, and death

Ca 380 - 450 ppm Calcium

Supporting the growth, skeletal structure, and shell formation of corals, mollusks, crustaceans, and coralline algae

KH 8 - 12 dKH Alkalinity

It acts as a shield, neutralizing acids to prevent dangerous pH "crashes" that can harm fish, corals, and plants.

Mg 1200 - 1400 ppm Magnesium

It enables coral growth by supporting skeletal formation, assists in metabolic processes, and ensures that calcium is available for corals, clams, and coralline algae.

SG 1.023 - 1.026 SG Salinity

Essential for maintaining stable, natural water parameters, proper osmoregulation, and stress-free environments for marine fish and corals

ORP 250 - 400 mV Oxidation-Reduction Potential

A higher positive mV indicates clean, oxygen-rich water with high water quality, while low readings indicate high pollution.

About Pacific Redfin Butterflyfish

General information

The Pacific Redfin Butterflyfish, or Lunule Butterflyfish, is a relatively small species, growing up to 6 inches (15 cm) in length. It has a deep body and a pointed snout with a mouth that is small and protrusible. This species is known for its striking black, white, and yellow coloration, with a distinctive crescent-shaped marking on its head. The Pacific Redfin Butterflyfish is a peaceful fish that can be kept in a community aquarium with other non-aggressive fish.

Diet & nutrition

In the wild, the Pacific Redfin Butterflyfish feeds primarily on small invertebrates and zooplankton. In an aquarium setting, it can be fed a diet consisting of high-quality flake or pellet food supplemented with frozen or live brine shrimp, mysis shrimp, and other small meaty foods.

Determining sex

There is no visible difference between males and females of this species.

Breeding & spawning

Pacific Redfin Butterflyfish has not been bred in captivity.

Diseases

This species is generally hardy and resistant to disease, but it is still susceptible to common aquarium diseases such as ich, velvet, and fin rot. Keeping the aquarium clean and maintaining good water quality can help prevent these diseases.

Origination

The Pacific Redfin Butterflyfish is found in the Western Pacific Ocean, ranging from the Philippines to Japan and south to Australia.

Cautions

The Pacific Redfin Butterflyfish should not be kept with aggressive or territorial fish, as it is a peaceful species that can be bullied by more aggressive tankmates.

Acclimation process

When introducing the Pacific Redfin Butterflyfish to a new aquarium, it is important to acclimate it slowly to prevent shock or stress. This can be done by slowly adding small amounts of water from the aquarium to the bag or container holding the fish, gradually increasing the amount over a period of time.

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