Moorish Idols

 

There is only one species in the genus Zanclus and that is the Moorish Idol (Zanclus cornutus).  It is often misspelled Morish Idol missing one O.  These fish are very closely related to the tangs (Acanthuridae).   And I mean very closely related.  They behave much like tangs and even fight with their tails... even though they are lacking a spine on the caudal peduncle.  In general, thinking of their husbandry as that of a Acanthurid is fitting.

These fish are nearly always found in the wild swimming as pairs.  From an aquarium point of view and from an aquaculture point of view this is awesome.  We can collect them as pairs of fish!  Once in a while a smaller third fish is there, and in some instances they are found in groups (usually attacking food sources and overpowering other fishes).  As fragile and delicate as they appear, they are actually known for being bullys and have quite the strong temper/attitude.

 

These fishes are not imported in high numbers.  In fact, most wholesalers only have a handful of Moorish Idols.  They frequently come from Hawaii, where they are hand caught near the shore.  These fish have been sought after for many years.  Their striking patterns and body shape attract all sorts of hobbyists.  Unfortunately their track record in the hobby is dismal.

 

Moorish Idols were first being captive raised... well I don't know when.  But I do know that by 1999 there was enough success to generate serious aquaculture interest.  In MASNA's publication Marine Scene (1999) Dennis Gallagher (yes that Dennis!) published an article called "Report From The Philippines" and Dennis stated that if banning the collection of fishes were to take place the breeders would soon be ready to enter the market.  Not only enter the market but he stated they would be able to successfully compete with the black market!

 

So here we are 10 years later and it hasn't happened.  Why not?
Number one, collection wasn't banned.  Therefore you didn't have to raise them in captivity to get one.  But a bigger factor (in my opinion) was pricing.  These fish come from Hawaii... are collected in an ecofriendly manner... travel a short distance to the Los Angeles wholesalers... and have relatively little expense when compared to Indian Ocean fishes. 

The main efforts to breed and raise Idols came from some French scientists.  I can't confirm this, but I think one reason it was so popular in Europe was because of the cost of flying the fish from Hawaii made them much more expensive in the Eurpean market.  These efforts didn't really take off.  Instead, some success in raising the post larval fish took over.  Moorish Idols settle on the reef at a very large size.  They can be collected off reef in open water in large numbers.  From here they can be raised to market size in aquariums.  Side note- collecting them is much easier said than done... I tried.

 

Right now Moorish Idols are on the no-no list of most aquarists.  And for good reason.  They typically don't live more than 2 weeks in captivity, one of those weeks spent before the hobbyist even buys the fish.  However, this isn't as bad as it sounds.  Many fishes don't make it that long in the hobby.  What's worse is that for many Indo-Pacific fish there is great loss prior to making it into the US, more loss at the wholesale, and then finally some loss in retail stores.  Moorish Idols don't suffer those initial losses.  That is a very significant issue.  If we ship 100 clown fish from Indonesia to Salt Lake City and only 5 come alive that means we have the %5 strongest fish.  Chances are you will do well with those 5 fish.  If we ship 100 Moorish Idols from Hawaii to Salt Lake City, almost all 100 will make it here alive.  If 95 of them die in a week we're still left with the %5 strongest fish.  Many experts argue that the perception of Moorish Idols being difficult to keep is because they all die in the hands of aquarists, and not in the hands of shippers. 

 

For many upon many years the reasoning behind Idol deaths has been of food concerns.  Not enough worms.  Not enough sponge.  Missing special microinverts from the diet.  Needs seaweed.  Doesn't eat plankton.  Arguements to go around a plenty.  And, possibly for good reason.  These fish do seem to have special dietary requirements that haven't been fully described.

 

Moorish Idols get sick.  No doubt about it.  In fact numerous reports show them "bombing" a tank.  The Idol gets sick and it dies.  That seems bad but it is only the beginning.  For when they die they are often times carrying loads of pathogens which then enter the water.  The real problem in losing an Idol may not be losing the Idol, but then losing all your other fish in a matter of a few days.  A very risky situation (think sea apples).

So why do they get diseased?  A couple easy answers, and some tough answers.  First, they have scaless soft skin.  This is ripe for many parasites.  However, in the wild they don't come into contact with many parasites.  In home aquariums where everything is so condensed the parasites can't help but land on the fish.  The aquariums may just not be big enough. (don't think experts lose everything to disease, read here http://www.advancedaquarist.com/2006/7/aaeditorial/ )

 

This was ruled out years ago... but is now making a strong case.  The fact is some very large aquariums (thousands of gallons) are doing well with Idols.  Most of these tanks are in public aquariums.  Having a large tank size may be the key in reducing parasites, and providing the live rock growth needed to feed these fish. 

Ah, wait, not so fast.  I have kept an Idol I had for 2 years?  I'm almost embarrased to tell you where I kept it.  It was in my 29 gallon tank.  That tank NEVER had a single water change.  Was I just lucky?  Twice?  You would think so... if it hadn't been for the other hundreds of hobbyists who also kept Idols alive in small tanks. 

And the other part of that, big tanks for more live rock.  Well, some of these large tanks are Fish Only Tanks without live rock!  And some of these large tanks (withour without live rock) are typically fed foods that are of LOWER quality than what most hobbyists have. 

 

Another thought on why these fish don't do well in reef tanks is because they are only sort of reef fish.  Many Idols are found right near the shore in crashing waves and tide areas.  For this reason some people are trying to keep these fish in chaotic tanks filled with waves and water flow. 

As a side note, some people (including myself) learned the hard way that these fish are prone to dieing on pumps.  They have a tendency to swim right up into the flow... and get stuck right on the Korallia, VorTech, Tunze or whatever stream pump is available.  You may think pulse mode will save the fish, but you'd be wrong.  They are able to swim to the pump, but they lack the strength to swim away. 

 

The hobby is filled with them.  Buy the fish, take it home, dead in four days.  Again, this sounds really bad but they hobby is filled with these stories for many species of fish.  However, this one is way up on the list of "bad" because there have been few success stories to go with those failure stories.

 

Here is where this fish differs from the rest.  It has all the failure stories like everything else, but it has few success stories.  We know they can be kept in captivity.  Some have been kept for many years.  Some (reportedly) spawn in captivity.  But success has been limited.  I myself have kept a Moorish Idol for over two years.  I've had another go well over a year.  What was my secret?  I don't know, I've also had one die at about the 1 month mark (could not keep it away from the pumps).  In general, I do well with Moorish Idols.  Okay I shouldn't say I do well with them, I should say I do far better than most, but there is still a long ways to go. 

To sum up the success, some have been kept in small tanks for years.  Recently larger aquariums are having more success.  They have been captive raised, and tank reared.  But those efforts seem short lived and never really took off. 

In every major city and in every aquarium club out there you can find someone doing very well with these fish.  They all have their theories on why they are successfull... but no one has really found a method that holds up.

 

For years and years the thought was foods.  In fact one of our club member Gary Williams has owned a couple Moorish Idols and they have all done very well for him.  He has told me a million times (possibly exagerated) that the key is "spectrum pellets."  If I hear Gary tell me one more time to buy "spectrum pellets" I'm shovin' the bottle of food up his... you get the idea.

The trend now isn't that Moorish Idols are difficult to feed (Blundell 2007).  In fact I swear I can get any Moorish Idol to eat in captivity.  There are some foods that I see them take every time (crushed dainichi, freshwater mysis, ocean nutrition spirulina flake, and yes Gary's spectrum pellets, etc.).  If you have an Idol, I can get it to eat.  However, it hasn't been shown that these foods contain all the Idol needs.  That is hypothesised to potentially be the key.  They may be eating these foods but that may be like a human living off of icecream and donuts. 

A very popular article by Dr. Thaler in Coral (2007) documented the relative ease in keeping these fish.  It indeed sparked the interest of many hobbyists who had shunned these fish fearing them difficult to keep.  Dr. Thaler even states "Zanclus cornutus is, without a doubt, a beautiful inhabitant of the aquarium that can grow very old when conditions are right.  The only prerequisite is, of course, that the fish is healthy and not "damaged" when it is introduced into the aquarium."
That is some seriously strong language in support of these fish.  I for one, am not quite ready to agree with that. 

  

1) some hobbyists claim that having bright moon lights help Moorish Idols.  While the other fish sleep, and the bugs come out, the Idol will stay awake and hunt

2) there is some evidence that after buying an Idol you should keep your tank lights on for several days (Blundell 2008).  On the theory that at night they aren't eating I developed a plan for hobbyists to keep their tank lights on 24 hours for several days.  It may have helped.

3) You can get Idols to eat... I guarantee it

4) I'm not sure they are eating everything they need to eat

5) They live for many years in small tanks

6) They die within 1 week for almost every tank

7) As difficult as it is for me to think of Spectrum pellets as the key, it is hard to argue against a guy that has had great success

8) Large aquariums are showing success... with or without live rock

9) Disease, disease, disease.  It kills Idols

10) A dead Idol can disease and wipe out a tank

 

Some more random thoughts and information...

 

 

 

ps- I'm still adding to this post, and I'll be adding pictures later as well....

 

Agreed! The next SeaStar is slated for release - the first of Oct.

 

Kind of smart ass answer, but that is the truth.  I mean you can do all you can but I still don't have any secrets.  Maybe Connie does.  Listen, it is a risky fish.  It certainly can be done but I'd fear disease, pumps, and nutrition.  So tackle those issues before anything else.

 

Adam

Difference between raising tangs and raising gobies is huge.  That I could answer.

Difference between raising Idols and raising tangs is small.  So that is very tough to answer.

 

You know, right off... you've stumped me.  We can get fertilized tang eggs, producing larvae.  But other than some minimal success with Yellow Tangs I don't think any tang has been captive raised.  No one has taken larvae to juvenile.

 

You know what.  You'll have to ask me again sometime.  I don't think I know the answer to that.

 

Adam