Keeping The Mysterious Moorish Idol

Moorish Idols. Impossible to keep. Better left in the wild, right? Anyone that has been in this hobby for nearly any length of time has read...
  1. Moorish Idols. Impossible to keep. Better left in the wild, right? Anyone that has been in this hobby for nearly any length of time has read things like this or can at least recognize this iconic fish. Many of us grew up seeing this majestic fish in photos and documentaries. Whether seen schooling in Hawaii or casted as "Gill", the wise Moorish Idol from the beloved Disney Pixar film "Finding Nemo", this fish is quite desirable in the hobby. Sadly, The vast majority of these fish do not survive past a few months in the home aquaria.

    But is it really true that these fish are best left in the ocean and impossible to keep? Well, like any sweeping statement this is untrue -- but the overall (intended) message is largely correct; this fish is NOT for the beginner or intermediate fish keeper. For the devoted, experienced hobbyist that is willing to cater to its' needs it can in fact be kept "successfully".

    Photo by R2R member @Bubblewood

    I will begin by mentioning my experience with Idols. I have kept two over the past three years which is hardly a "success" if I am being honest. My first idol lasted two years before getting an eye infection. As fragile as idols are, unlike my prior fish to become "cyclops", he did not cope nor adapt. I noticed the infection too late and what was once the healthiest eater in the tank began his signature Moorish Idol downward spiral. They are notorious for "randomly" dying after a few weeks or months and randomly refusing to feed (permanently). I have quarantined and treated several (thus getting them to eat successfully) for local reef clubs on several occasions. I think I've quarantined 12 now, 11 successfully. My friends that have kept these fish for a couple years or more also follow the same "formula" to come. Important to note that an idol should live 10+ years in captivity to be truly declared a success, in my opinion. I believe I will get there.

    For most people that have attempted Idols, it generally ends one of two ways.

    1. You bring home your beautiful new fish and despite your efforts you cannot get the fish to eat. Slowly the fish wastes away and dies. You become frustrated.

    2. You bring home your idol and you are lucky enough to get it to eat. Despite a healthy appetite, it seems to continue to lose weight and waste away. Perhaps it doesn't lose weight but after a few weeks or months the fish drops dead. This is often due to feeding the wrong foods, not enough food, and parasites. I will discuss all of these things.

    So what do you do? In my opinion there are three primary factors that can lead to success for the experienced hobbyist with a well established tank.

    1) Start with a healthy specimen. This may sound like common sense but even seasoned hobbyists have difficulty identifying a healthy specimen from one not so healthy. To make matters worse, most LFS keep fragile fish in low amounts of copper which will mask the presence of parasites but will not rid the fish of them.

    Avoid fish that have spots, "dustings", torn fins, discoloration, erratic swimming or breathing, or are otherwise thin. An idol that has a clearly visible spine (not to be confused with the lateral line) is almost always a goner by that point. At this point of fasting they rarely if ever begin feeding. As a result, it is best to buy a fish that is already eating and feed it what it ate at the LFS. Buy a very fat idol whenever possible as this gives you the best chance of success. Consider the extra weight as extra time you have to get the fish to feed. In general, a thick fish is also a sign of an overall healthy specimen, though not commonly found after going through the distribution system.

    My two idols were purchased from NYAquatic and Live Aquaria's Divers Den. I trust these sources and they do a fine job but there may be others.

    Photo by R2R member @foxvalleypcgeek

    2) Provide a disease-free environment. This is a fish that will need to go in to a tank where every fish has been properly quarantined AND treated for ich/velvet/flukes as a precaution before addition. The idol will also obviously need to be treated using the same regimen. There are many fish in this hobby that may tolerate "ich management" practices whereby you do not quanrantine or treat fish prior to addition. The Moorish Idol is NOT one of these fish. In today's environment disease is more prevalent than ever and this practice is probably the single most common reason for people exiting the hobby and fish deaths.

    Although your fish may not show symptoms, if you do not properly quarantine and treat they are carriers that have built up a resistance to parasites. This will become starkly obvious when adding fish like Moorish Idols, powder blue tangs, achilles tangs, other acanthurus tangs, or other fragile species.

    The deck is already "stacked" against you with this fish, the last thing you need is another stressor/factor weighing down your chances of success. With idols, weight is everything. With ich or other parasites present, too much energy will be spent fighting these infestations off and eventually they starve and die. They have very high metabolisms and need lots of calories to be retained to thrive. This is a great segway in to the next factor.

    Two idols I am currently quarantining (but will not be kept together post-quarantine). Both eating nori, live blackworms, fresh mussels, and some frozen foods.

    3) Diet is critical. In the wild, Moorish Idols dine on sponges, algae and other marine plants, and even some corals (such as polyps). Many have written that they feel that high quality pellets such as "Spectrum pellets" are the secret to idol
    success. I have never fed any of my idols these foods so I cannot comment. Like many angels, sponges are largely omitted from their diet in the home aquaria and are actually a very important staple. Hikari and Ocean Nutrition both have a frozen "angel formula" that contains sponge. To get them to start eating, fresh mussels are a good choice. Break in half and leave one half in the tank. Even more important than sponge and often ignored is nori. As I said, the key to idol success is to have a thick, well-fed fish. This can obviously be difficult if they do not eat. Red nori is the often overlooked staple of their diet and in my personal opinion is the single most important food for your idol. Nori is important because they can get a lot of calories and girth. Also, grazing throughout the day seems to be soothing for a fish that grew accustomed to this in the wild. Since stress can be such a killer, reducing stress is a good idea. In my opinion, leaving nori for them serves a dual purpose. Mine get equal amounts of red and green nori. For finicky eaters, try rubber banding nori to a small rock so it can best resemble wild feeding habits at first.

    My fish all get a mixed smorgasbord of a dozen or so frozen foods (including lots of angel formula) that are mixed, strained, and soaked in selcon. I add garlic guard when I am trying to tempt new fish to eat as well. They also have access to nori for most of the day, whatever amount that requires.

    For the struggling idol try fresh mussels, live blackworms, red nori, and live brine. These can tempt even the most finicky or hesitant eaters. Blackworms are also a very nutritional food and should be fed to marine fish regularly.

    Other Factors

    1. Moorish Idols do not prefer to be kept in pairs. This is often perpetuated on forums I suspect in part because people see videos or photos of them schooling in the wild. However, many fish such as the powder blue tang school frequently in the wild but do not get along or have enough room in the home aquaria for this behavior.

    2. Moorish Idols should have access to enough nori that it is gone by about midday or longer. This allows them to graze for about half of the day.

    3. Idols, in my experience, are not particularly sensitive to medications. I've successfully treated about a dozen with copper at high dosages without issue. It's best to get them eating healthily before treating if possible. If visible disease is present then begin treating as soon as possible.

    4. Idols should not be kept with aggressive fish as stress can be a quick killer. They are relatively fragile fish. When stressed they tend to stop eating and this is typically a death sentence as they don't generally begin eating again after they have decided to quit. My idols have been with large angels, a couple tangs, and large wrasse which seems contrary to my suggestion. My angels are not very aggressive and have respected both idols. However, I do not recommend anyone do as I have. If aggression were to become a factor I have two other tanks I could move the idol to without issue.

    5. Moorish Idols prefer at least 5 feet of swimming room with 6+ being ideal. They can cover vast distances in the wild and to reduce stress a larger more established tank will be best.

    Please do not attempt this fish if you cannot commit to the above suggestions. Can you succeed without all of them? Sure, but your chances will be greatly reduced and another treasure of the ocean may be wasted.

    Happy reefing!


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    About Author

    Jason has been keeping saltwater fish and reef since 2004. It began with a job at a pet store that quickly turned to an obsession. He has made every mistake in the book and within 6 months had four aquariums and has maintained no fewer than three over the years at any given time.

    A tang, angel, wrasse expert and difficult to keep fish enthusiast, he consistently pushes the limits to learn more about fish. His prized fish include a pair of Achilles tangs and a pair of Red Sea Regal Angelfish. Jason also frequents the disease thread as he has learned a lot over the years he hopes to share. Jason spent the first 10 years in this hobby practicing "ich management" techniques which he no longer recommends.

    Outside of this hobby, Jason is a Ford fanatic with, you guessed it, 4 Fords in his garage. He works in the finance industry, specifically in the unique position of setting up wealthy Americans with reverse mortgages as financial tools. He has two children; a boy and a girl, and is an Indiana University (Kelley School of Business) and Butler University MBA graduate.
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