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Moorish Idol

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Moorish Idol Photo by Sam Wong
Guide Care Rating
  • Juveniles - 2 Stars
  • Adults - 3 Stars

Family: Zanclidae

Scientific Name: Zanclus cornutus (Linnaeus, 1758), but also found in books as Z. canescens.

Identification: The Moorish Idol is not an Angelfish, nor a Butterflyfish, but rather a close relative of the Acanthruidae or Surgeonfish family. A one-of-a-kind Zanclidae family member, this fish is also often misidentified as a Pennant or Bannerfish, which are actually species of the Heniochus genus that are commonly referred to as the "False" or "Poor Man's" Moorish Idol.

Distribution: From Hawai'i to Australia, and from the west coast of Central America westward to the coast of Africa and the Red Sea.

Average Size: Generally to about 7 inches, but some adults may attain 8 or 9 inches.

Habitat: Should be provided with plenty of unobstructed swimming space, as well as ample hiding places to take refuge when feeling threatened.

Minimum Tank Size Suggested: 100 gallons.

Characteristics and Compatibility: Typically the Moorish Idol is a moderately-peaceful fish best kept with other non-aggressive species. In regards to keeping multiple numbers of these fish together, there are many opinions. Some aquarists recommend only keeping this fish singly or in mated pairs, while others suggest they only do well if introduced into an aquarium in groups of four, six, ten, or whatever.

From experience we know that large mature adults have a low tolerance for one other, and therefore keeping a single specimen or a mated pair is recommended. As far as juveniles, although this fish does seem to commune fairly well as a group, nonetheless their behavior towards one another can be "unpredictable". Sometimes a group of smaller Moorish Idols will get along just fine, while other times there may be one renegade in the group that becomes dominant, and decides to pick on all the others.

Diet and Feeding: Typically difficult fish to keep, larger specimens usually do not adjust well to aquarium life. With the tendency to ignore foods offered, most often their health will decline due to slow starvation. Smaller juvenile or sub-adult specimens may more readily adapt to their surroundings, but just the same, these fish are unpredictable in their feeding behavior.

For fish that refuse to eat, to survive in captivity live rock that is rich with coralline algae and sponge growth may be needed to stimulate their desire to do so. Offer finely chopped fresh or frozen shrimp, clams, squid, and other meaty fares suitable for carnivores, live mysid and brine shrimp, some vegetable matter as well as supplemental vitamin-enriched prepared foods that contain marine algae and Spirulina. Feed 2 to 3 times a day.

Reef Tank Suitability: Moorish Idols will often pick at LPS corals, and certain soft coral polyps. Although this fish primarily eats coraline algae and sponge in nature, this doesn't mean that it might not pick at other types of sessile invertebrates, or maybe even motile crustaceans.

Guide Buying Tips: Because these fish are typically difficult to care for in captivity, a key factor in the success of keeping a Moorish Idol is buying one that is in the best of health to start with. Here are some important things to observe and find out about this fish, before you decide to buy one.

  • The colors should be dark, and bright, not faded or washed out.
  • The fish's body should appear somewhat full and rounded out at the sides, the stomach area should not appear concave or sunken, and the skeletal structure of the fish should not be noticeable underneath the skin.
  • Ask someone to feed the fish while you are at the pet store. If they will not, because they may have set feeding times, find out when this is, and then ask to be present so you can see for yourself that the fish is eating well.
  • Find out what the pet store is feeding the fish, and match that diet.
  • If the fins and the tail appear to be frayed or ragged looking, or are partially burnt off around the edges, and the fish's eyes are cloudy, this is most often a sign of exposure to ammonia burns, which usually stems from bad collecting and shipping practices, but can also result from poor aquarium water quality conditions and care.
  • One of the best gauges for judging how this fish has been handled is to look at its long white streamer or pennant. If it is partially missing, or burnt off altogether, it's a sign the fish was at one time, or may be exposed to unfavorable conditions. However, if the streamer is missing, but you can see a new, small white filamentous-like growth starting to grow out of where the pennant used to be, its an excellent sign that the fish is getting the proper care, recovering and regaining a state of good health. Now if the pennant is missing, but no new growth is yet apparent, its a good idea to wait a week or two to see how the fish's condition progresses. It is not unusual for the symptoms of exposure to ammonia burn to be delayed, therefore a particular fish's condition can possibily decline as well.

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