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Fish Profile - Chelmon Muelleri

Meuller's Butterflyfish - Chelmon Muelleri

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Mueller's Butterflyfish, Chelmon muelleri

Photos courtesy of Michael G. Moye. 
Meuller6 Meuller1 Meuller3


Common Name: Mueller's butterflyfish, Blackfin coralfish, or Muller's coralfish
Scientific Name: Chelmon muelleri (Klunzinger, 1879)
Size: Up to 8 inches (20.5cm)
Distinguishing Features: Like most from the genus of Chelmon, the Meuller's butterflyfish have an elongated tubular snout that is used to pry into small crevices looking for prey. They have four vertical bars on their body. A false-eye spot is located on the rear dorsal fin to aid in escaping predation.
Distribution: Pacific Ocean: Found exclusively near coral reefs and estuaries of Northern Australia.
Natural Habitat: As benthic feeders they prefer mud bottoms of estuaries and coastal reefs. Indigenous to Northern Australia only. 
Feeding Requirements: It is not difficult to imagine the feeding requirements of this species. Considered a benthic feeder its long snout is perfect for hunting small sessile invertebrates. Will nip at featherdusters and possibly will eat clams and Aiptasia. Upon receiving this species it is advisable to get it feeding on live mysis, blood worms, or other similar food. Initially they may refuse commerical feed. Therefore they should be fed a variety of live foods and slowly converted to frozen or flakes. Nutrition is a concern with this species and a variety of foods should always be offered.
Difficulty Rating:
(1 = easy - 5 = hard)
The difficulty rating of 4 out of 5 is deserved. Due to stress from shipping, their malnurishment and possible infections may have the greatest impact on survivability in captivity. The most difficult aspect of this specie is having it feed regularly when initially received. Once established and regularly feeding in a stable high-water quality aquarium they will last for many years.
Aggressiveness Rating:
(1 = shy - 5 = nasty)
The Mueller's butterflyfish is a model citizen and receives an aggressive rating of 2 out of 5. Similar to that of the Copperband, they are shy and timid feeders. When housing with larger more aggressive species, it is advisable to introduce these animals first.
Captive Requirements: Inactive at night, this animal spends its day foraging around the open reef. In captivity this should be no different and the Mueller's butterflyfish deserves a tank of no less than 100 US gallons (380 liters). This animal can reach sizes of 8 inches and ideally should be kept in 150 US gallon aquariums or larger (570+ liters).
Reef Tank Compatibility: This fish fits the profile of many Chelmon species. It should be introduced with caution similarly to that of Chelmon rostratus (Copperband butterflyfish) and Chelmon marginalis (Margined coralfish).
Personal Experience:

I once read an article that referred to it as the Copperband's, Chelmon rostratus, 'ugly stepsister'...  Now maybe it's me, but with its burnt orange stripes alternating on a mother-of pearl background, I'm already sold on the Mueller's in terms of asthetic appeal. But add the electric blue and yellow specklings within its fins and flanks, its foreshortened snout, amusing personality, and refreshing hardiness and it's absolutely no contest.

Anyway, as I'm sure you know, these fish are endemic to Australia. Now while some would cite this as a reason for their hardiness, I tend to give credit to the country's superior capture and shipping techniques rather than to anything inherent in the animal itself. Still, they are not exported very often and when they DO turn up, they usually command a pretty high price.

While I've never had a real problem getting Mueller's to eat, even during acclimation, I'd always start them with clams, oysters, or mussels on the half-shell. Nowadays, I use live California blackworms, which they simply cannot resist. My Mueller's also loves Mysis soaked in Selcon and I usually feed twice a day. I've heard they will take out your feather dusters, zoas, and pick on clams but since I do not maintain any of the three in my display tank, I cannot comment on that with any first hand knowledge. I DO know this however, given the chance they will simply decimate Aiptasia! You can even train them to do this in QT (quarantine) by providing an Aiptasia covered live rock, 'starving' the fish for a day, then feeding the ANEMONIES a bit of mysis (or whatever the fish has grown to like)! In many cases, the butterfly will quickly grow weary of watching the Aiptasia eat its dinner and take appropriate action. If you run into a stubborn one, you may have to do this more than once but sooner or later, they learn to associate the pests with food thievery and then as food themselves. My first Mueller's (I've had two myself and acclimated a third for a friend) even took out my Majanoes after this method.

They are the only butterflies I've kept in a reeftank so I also cannot comment on how they would get along with other butterflies. My duo of Purple Tang and Striatus Bristletooth usually comprise the welcoming committee in my current tank but so far the Mueller's has more than held it own against them both. This, by the way, is why I strongly recommend these fish be QT'd before introduction to the display tank. Not that they're any more prone to disease than other fish, but simply to build up their strength. When I first added my current Mueller's, the tangs kept it pinned in a corner for nearly a week. Unless it picked at the live rock after lights out, I never saw it eat during all that time. Obviously, the tangs gradually lost interest and accepted the fish into the group but I doubt it would've survived that first week at all had I not given it the time to build up its reserves in QT.

It probably goes without saying this is probably my favorite fish in the tank. In addition to earning its keep, its personality, smarts (it will literally 'follow' me back and forth the length of the tank at feeding time while paying no one else any attention whatsoever), and penchant for entertainment (see, head-on portrait shot) can almost make it a one man show in any suitably sized tank. It's not easy to find one, but if you do, do NOT hesitate for a second.

-Michael G. Moye

Further Reading: Fishbase.org - Chelmon muelleri

Note: All of the above information has been compiled from various sources and should be used as a guideline, not a hardfast rule. Use caution when selecting animals for your own tank and research as much as possible before purchasing any animals. Remember that certain corals and fish are very hard to keep if their special requirements are not met. The information contained here is to help you make an informed decision. The author assumes no responsibility for any consequences that may arise from the use of this information.

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