That Fish Blog – Aquarium Advice and Information

Large, flashy, uniquely-shaped and active, Silver Monos, Monodactylus argenteus, always draw attention when seen for the first time.  But there are many misconceptions concerning their proper care, and new owners often become frustrated with them and move on to other interests.  However, when their unique needs are met, Monos are quite hardy and make for spectacular exhibits.  A group I cared for at the Bronx Zoo, housed with Mudskippers, Fiddler Crabs and Banded Archerfish, proved so interesting that they rivaled neighboring Leaf Insects, Hornbills and Tapirs for visitors’ attentions.

Uploaded to Wikipedia Commons by Brocken Inaglory

Description

The Mono’s silvery coloration shimmers under light, and is nicely offset by yellow or black fin tips and the jet-black stripe that runs along the edges of the dorsal and anal fins.  The body is flattened and disc-shaped, and the sturdy dorsal and anal fins are much-elongated.  Silver Monos are powerful swimmers, well-able to buck the strong currents common to the tidal rivers and coastal mangroves that they frequent.  If given enough space and a proper diet, they can reach 9- 10 inches in length, but most in the pet trade top out at half that. Read More »

Hello, Frank Indiviglio here.  In the early 1980’s, I had the good fortune of being chosen to help set up the exhibits in Jungle World, a new Bronx Zoo building highlighting Southeast Asian wildlife. Leaf Insects, Sunbirds, Marsh Crocodiles, Giant Soft-shell Turtles, Proboscis Monkeys, Tapirs…all came under my care, but it was a mangrove marsh exhibit that became my favorite. It housed a variety of unique animals, including Mudskippers, Fiddler Crabs and Monos, but the real stars were a school of Banded Archerfish (Toxotes  jaculatrix).  Visitors especially enjoyed watching me service the exhibit…the Archerfishes would invariably squirt water at the movement of my eyes as I looked down at them, and they never missed!

Natural History

Seven archerfish species have been described. They range from India to Malaysia and Australia, ofrten in association with brackish water mangrove swamps, but most also enter freshwater and the ocean. Archers and other species that move between salt and fresh water for other than breeding purposes are known as amphidromous fishes. 

At least 1 species, the 5 inch-long Smallscale Archerfish (Toxotes microlepis), spends most of its time in the freshwater. The giant of the genus is the 16 inch-long Largescale or Spotted Archerfish (T. chatareus). Both occasionally appear in the pet trade, where they are often confused with the Banded Archerfish (please see below). Read More »

Hello, Frank Indiviglio here.  This Southeast Asian fish’s slender, 3-inch- long body belies its reputation as a fearsome combatant.  However, in betting parlors from Thailand to the Sunda Islands, matches between male wrestling halfbeaks (Dermogenys pusilla/pusillus) rival those featuring the better-known bettas (Betta splendens) in popularity.  In contrast to bettas, battling halfbeaks rarely inflict any serious damage…other than to the billfolds of losing gamblers!

Description and Habitat

Halfbeaks sport a startling adaptation to surface feeding…their immobile lower jaw is more than twice the length of the upper.  This, along with their subtle beauty – a silvery body highlighted by hints of blue and green – renders them a most unique addition to one’s collection. 

Halfbeaks inhabit estuaries and other areas of fluctuating salinity, and, while sometimes kept in fresh water, are at their best in brackish water aquariums. 

Feeding Wrestling Halfbeaks

Halfbeaks are highly specialized surface feeders and rarely if ever swim to lower depths in the aquarium. They tend to be picky feeders and prefer tiny live invertebrates such as mosquito larva, brine shrimps, fruit flies and Daphnia. Chopped blackworms may be taken, but these sink quickly and so must usually be offered via forceps (tedious but effective!). 

Halfbeaks may be habituated to flake and frozen foods, but the progeny of such fishes rarely reproduce, most likely due to a nutritional deficiency.

The Halfbeak Aquarium

While visiting pet stores and aquariums in Japan, where halfbeaks are more commonly kept than in the USA, I was surprised to find that multiple males were often housed together.  I learned that males will co-exist in large, well planted aquariums if emergent and surface-dwelling plants are grown as sight barriers.  Watching the threat displays and interactions in such aquariums was most interesting, and cast these little fellows in a new light for me.

A unique habitat preference and feeding style dictates that halfbeaks be kept in long, shallow aquariums and, with few exceptions, in single-species groups.

Breeding Halfbeaks

Wrestling Halfbeaks are live bearers, with healthy females giving birth every 30 days or so; males may be distinguished by a bright red blotch located in front of the dorsal fin. 

Unfortunately, adults are quite cannibalistic, and the fry rarely survive.  Breeding traps are not recommended, as the birthing process takes several days and females become stressed by long confinement in small areas.  Thickly-planted aquariums, with much of the vegetation at the surface, offer the best chance of success. 

Further Reading

Detailed information on the natural history of these and related fishes is posted at ZipCodeZoo.com.

A book I’ve written, The Everything Aquarium Book, addresses the care of brackish water fishes in detail.

Please write in with your questions and comments. 

Thanks, until next time,

Frank Indiviglio

Halfbeaks image referenced from wikipedia and originally posted by Neale Monks