By Bob Goemans
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Triggers in My Aquariums

Authored by: Bob Goemans

First printed in TFH, July 2007

The Family Balistidae (Triggerfishes) contains ten genera and 40 species, with few suitable for the average home aquarium. Like angelfish and surgeonfish, they have laterally compressed bodies and small mouths, but have strong jaws and chisel-like teeth for crushing hard-shelled prey. Their scales are plate-like and have no pelvic fins, however, there is a pelvic spine. And there are three dorsal spines; yet, in some species the third spine is underdeveloped. They are carnivores and their diet consists mainly of small fish, starfish, crabs, shrimp, snails, and are especially fond of urchins, which makes them a ‘fish-only’ aquarium inhabitant, or at least one without tasty inverts!

Their head often takes up a third of their body length and contains well-developed and independently moveable eyes, which are set high up on their body to protect them from urchin spines. In fact, besides being very capable at breaking off urchin spines so as to get to the central meaty body area, they are also capable of expelling a jet of water from their mouth to turnover urchins so they can get at their soft underbelly! In aquaria, should their diet be inadequate, they tend to lose their vivid colors; yet will normally be paler when resting during nighttime hours. They should be housed with small pieces of seashells on the sand bed surface since they like to bite on them or turn them over in the search of prey. Better these shells being their ‘toys’ than other aquarium décor! And besides, it helps keep their teeth worn-down, which actually could get too long and pointed and cause them some difficulty in feeding.

Their common name comes from their ability to lock and unlock their first dorsal fin. This fin is normally retracted and carried in a groove on the upper body. When frightened, the fish will dart into a crevice or branch of coral and raise this trigger-like fin, securely locking itself into its place of protection. This first raised and locked spine can only be released when the second spine is depressed into its recess. Normally, they rest at night on rock ledges, amongst coral branches and/or in caves and crevices. They also have a unique form of swimming where the anal and dorsal fins are used for most of their movement; nevertheless, when bursts of speed are needed they use rapid movements of the tail.

These fishes appear to be quite intelligent besides being very hardy and beautiful, however, most are quite pugnacious and some have been known to attack divers when they got too close to their territory. Most are better kept with large moray eels, snappers, angelfish, and tangs, as they can’t be trusted with smaller tankmates. Definitely a fish with a personality!

Because of their aggressiveness, I’ve kept very few that I would select a second time, yet the ones I did maintain are worth mentioning, as is one species that I would not put into an aquarium with ‘any’ tankmates. Or as a matter of fact, into any aquarium that I would no longer want to use as it can even destroy its viewing panels, but more about this one later on in this article.

Lets begin with my personal favorite, which has been in a variety of my different style aquariums, and that’s been Odonus niger, the Black Triggerfish, Blue Triggerfish, Red-toothed Triggerfish, Red-fang Triggerfish, or often simply called the ‘Niger’ Triggerfish. It hails from the Indo-Pacific: Red Sea to Durban South Africa, Marquesas and Society Islands, and southern Japan to the Great Barrier Reef and New Caledonia, where it normally inhabits shallow coastal waters to outer reef drop-offs at depths of 30 to 100 feet (9 – 30 m) and where it reaches a length of about 20 inches (50 cm). Yet most of what I’ve seen in the trade is far smaller, with sizes varying from an inch (2.5 cm) to about 8 inches (20 cm), which is the largest I’ve ever seen at local shops.

In more mature members, the teeth are really red, and its body coloration seems to depend on lighting and the time of day, as its usually blue, but sometimes appears bluish-green or a dull green color. Its large head area is paler than the rest of its body, making it standout and which is also highlighted with blue lines and dots around the snout. Its tail also has long filaments on the upper and bottom tailing edges. For some reason, I’ve called this my “Darth Vader” fish, as it seems to have an uncanny ability of awareness about it. It was always either visible or not at just the right times, and when it came time to eat, was not to be denied its share of the food! I’ve always purchased this beauty fairly small, e.g., less than 3 inches (7.5 cm) and always housed it with tankmates at least its size, as it would consider anything smaller a dinner. In fact, its been kept with large angelfish, surgeonfish, moray eels, and even lionfish, which even though a much slower swimmer, was always capable of successfully fending off any interest in its fins by the triggerfish. Nevertheless, the triggerfish had to be fed first, as it was the quickest in these tanks.

Hardy might be an understatement, and bulletproof another, but easily a specimen that is not fussy about water quality or most tankmates, with the exception being others in its own family, as one triggerfish per tank is the general rule. And when it came to its diet, anything meaty was just perfect, and I often brought back urchins from my trips to nearby Mexico waters to just watch my Darth Vader’s go through its feeding antics. In between, I fed enriched defrosted pieces of fish and shrimp flesh, and mollies when available. And I should note, information has come to me recently that seawater raised mollies may now again be available, which would be a perfect live food for these carnivores and lionfish (

Another favorite has been the Clown Triggerfish Balistoides conspicillum, which attains a length of about 20 inches (50 cm) in the wild. It hails from the Indo-Pacific Ocean: East Africa south to Durban South Africa, Indonesia, Samoa, southern Japan, and New Caledonia, where it swims in open deep drop-off areas, yet seeks local caves areas to hide in. Without a doubt, a very beautiful fish where the young have large white spots over most of its body and head, and a yellow snout area. As it matures, a yellow saddle area starts to develop around the first dorsal fin and contains small bluish spots. The yellow on the snout recedes to just a small area around the mouth and is bordered by a white line. The few specimens I’ve kept over the years were all about 6 inches (15 cm) or slightly smaller and had their mature color pattern.

They were maintained in systems no smaller than 125 gallons, and their tankmates were generally tough damselfish, large surgeonfish and moray eels. Clowns can be considered somewhat aggressive, and not, and let me repeat that, not to be trusted with anything very small or having a meek disposition! In fact, one of my sergeant major tough damselfish brought back from Mexico waters went missing a week after a Clown was added! I never did find out what happen to it, but it could have been the octopus that slipped into that 320 gallon tank from some live rock brought back from some tide pool trips to Mexico (another story for another time!). Its requirements are the same as the above-mentioned species; however, Clowns should have large open areas for swimming.

The Blue Throat Triggerfish, Xanthicthys auromarginatus, which attains a length of about 8 inches (20 cm) in the wild, can be considered quite mild temper wise, when compared to others in its family. It hails from the Indo-Pacific Ocean: from South Africa north to the Ryukyu Islands and east to the Hawaiian Islands. I’ve had this species twice, and both times my 3-inch (7.5 cm) specimens were quite mild mannered and well behaved and did well in mixed company. Another that was also well behaved was the Pinktail Triggerfish Melichthys vidua, which hails from similar areas, yet gets quite a bit larger at 14 inches (35 cm). Both of these were purchased quite small, about 2 – 3 inches and actually made good tankmates and can be considered the more gentle, better mannered of those in the entire triggerfish family.

I’ve had a few triggerfish that were outside my comfort zone, as they were not completely trustworthy even in mixed company of larger fish. The first is called the Picasso, White-barred, Hawaiian Triggerfish Rhinecanthus aculeatus, which inhabits most of the worlds tropical seas, e.g., Red Sea and South Africa, east to Hawaiian, Marquesas, and Tuamotu Islands, southern Japan, Lord Howe Islands, and also the Eastern Atlantic Ocean – Senegal to South Africa, making it one of the more plentiful triggerfish, therefore generally the least expensive. It reaches a 10-inch (25 cm) length in the wild, and is one of the few triggerfish that will tolerate others of the same species in the same tank; however, they should be added as juveniles if this is to be tried and preferably at the same time. An odd thing with this species is that it can be heard sleeping! Yes, …it snores, i.e., actually emits an audible whirring sound while sleeping! (Actually my wife does the same thing, but she doesn’t believe it!) The second, similar size and coloration, is the Rectangle Triggerfish, R. rectangulus, coming from the same areas except the Atlantic region, and a third, also somewhat similar in size and coloration, except that it hails from the Western Indian Ocean, i.e., Red Sea to the Gulf of Oman and the Persian Gulf, is the Assasi/Arabian Picasso Triggerfish R. assasi. All three had basically the same diet and temperament, but liked to rearrange system décor, chew on my temperature sensing and probe leads, and take a shot at a passing fin on a larger tankmate! Keep in mind not all my aquaria had a sump, where relocation of some of those items was possible, so it was a lesson learned where I was concerned.

Probably the biggest mistake I made was with the Blue-lined Triggerfish, Pseudobalistes fuscus, which can get quite large in the wild, e.g., 18 inches (45 cm). It hails from the Red Sea to Durban South Africa, Society Islands, southern Japan, Great Barrier Reef, and New Caledonia where it generally inhabits deep reef outcrops. This very pretty fish was purchased quite small and placed in a large 220-gallon system with much larger tankmates. Unfortunately this tank did not have a sump, and when I found this fish taking bites out of my heater cable cord (after it ate every snail in the aquarium), that was the last straw! It wasn’t easy getting it out of that aquarium, but it went back to the local shop for credit towards another purchase!

Before I close, it’s a must to mention Balistapus undulates, the Undulate, Orangelined, Orangetailed/Yellowtailed Triggerfish, which gets to about 12 inches (30 cm) in the wild. It hails from the Indo-Pacific Ocean: Red Sea to South Africa, Line, Marquesan, and Tuamotu Islands, southern Japan, Great Barrier Reef, and New Caledonia. This is an easy beauty to identify, as it has a yellowish-orange tail with undulating orange lines on a dark green body. The word ‘aggressive’ does not do this fish justice! A ‘terror’ or ‘demon’ might better suit it. Then again, the word ‘ferocious’ might better suit it! In fact, it’s such an aggressive fish that it can’t be safely kept with anything but itself! And I should note that a good friend kept a full-grown specimen in a 75-gallon all glass tank in his shop. If you placed your hand near the tank panel, it would attack the panel, which was well disfigured with gouge marks from its teeth! A pretty fish, i.e., pretty terrifying! Not something for your home aquarium with tankmates of any size unless you’re planning on using them as live food!

Another two in this same ‘terror’ category that are unmanageable in my opinion in mixed surroundings is the Titan Triggerfish Balistoides viridescnes, and the Queen Triggerfish Balistes vetula. The first gets to about 30 inches (75 cm) in the wild and actually attacks divers, and the second, about 20 inches (50 cm) in the wild and will rearrange aquarium décor, bite airline tubing, possibly break heater tubes, and also scratch aquarium side panels.

In closing, my favorite has always been the ‘Niger’ Triggerfish Odonus niger, and as for two somewhat even more mild mannered triggers, the Blue Throat Triggerfish, Xanthicthys auromarginatus, and the Pinktail Triggerfish Melichthys vidua can be considered quite well behaved in mixed company. Yet none should be considered safe with smaller fish or tasty invertebrates such as shrimp, snails, and urchins, as they will be considered breakfast, lunch, or dinner! Choose well before adding one to your aquarium!

Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Tetraodontiformes

Suborder: Tetraodontoidei

Families Balistidae (Triggerfishes); Monacanthidae (Filefishes); Ostraciidae (Trunkfishes); Tetraodontidae (Puffers & Tobies); and, Diodontidae (Porcupinefishes & Burrfishes)

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