Mertensii Butterflyfish

 Quick Care Facts

• Care Level: Moderate   • Temperament: Peaceful   • Maximum Size: 6"
• Minimum Tank Size: 75 gallons   • Water Conditions: 72-80° F, dKH 8-12, pH 8.1-8.4, sg 1.020-1.025
• Diet: Omnivore   • Origin: Indo-Pacific, Central Pacific
• Family: Chaetodontidae   • Species: Butterflyfish   • Aquarium Type: FOWLR

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Mertensii Butterflyfish, also commonly referred to as Merten's Butterflyfish, Orangetail Butterflyfish, and Atoll Butterflyfish,. They are a striking species that actually has two scientific names relative to its area of origin (Chaetodon mertensii and Chaetodon madagascariensis). Mertensii Butterflyfish can be found among the coral reefs throughout the tropical areas of the Indo-Pacific to Central Pacific waters. As with most of the Chaetodontidae family, the Mertensii Butterflyfish may not eat for a while during acclimation to a new aquarium; live food is suggested to get them started.

Mertensii Butterflyfish should kept alone or in a pair as they can become aggressive and territorial towards others of their species as well as other Butterflyfish of a similar appearance; they are not aggressive with heterospecific tank mates and can be very peaceful, but Butterflyfish should never be kept with tank mates that are prone to bully others. Mertensii Butterflyfish demand high water quality and current in order to thrive in the home aquarium and should be kept by moderately experienced to expert hobbyists and only be added to established systems where their needs can be met.

Mertensii Butterflyfish require open swimming space and should be housed in aquarium of at least 75 gallons while a pair should be kept in a 90 gallon or larger setup. They prefer a sand substrate and plenty of live rock caves and crevices for territory, security and shade. Strong and efficient biological and mechanical filtration is required as well as protein skimming to ensure excellent water quality, which they demand. In addition to highly oxygenated water they also need a moderate to high level of current in their environment. Lighting intensity should initially be subdued during their introduction (the first few days) to a new system as they are naturally a nocturnal species that can sometimes be difficult to acclimate.

Mertensii Butterflyfish are peaceful and get along well with many other marine species, although they are known to be aggressive and territorial towards conspecifics and similar looking species; although not many fish species will bother Butterflyfish, tank mates should not consist of overly aggressive or territorial fish that may bully them. They should ideally be kept in a FOWLR setup as they are not reef safe and are known to eat anemones, stony corals, sponges, and some invertebrates.

Mertensii Butterflyfish are considered to be omnivores, but a large part of their natural diet mainly consists of meaty foods such as anemones, coral polyps, benthic invertebrates, and sponges. In the home aquarium they should be fed a wide variety of meaty foods such as live, frozen, and vitamin enriched brine shrimp, mysis shrimp, krill, chopped clams, mussels, crab meat, sponges, the occasional anemone, and other meaty marine foods. They can eventually be conditioned to accept freeze-dried and other prepared foods once they start eating regularly and should then be introduced to high quality, Spirulina-based pellets and flakes, marine algae and other food items with vegetable matter. Feeding should be 1 to 2 times per day and only what will be consumed within a few minutes.