That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here.

The subjects of this article are often sold in pet stores as “curiosities” to be added to aquariums housing typical tropical fishes.  Unfortunately, due to their unique dietary requirements and feeding methods, none do well in such situations.  As most hobbyists are unaware of their fascinating behaviors, tanks are rarely set up solely for these creatures, and most perish in short order. 

I recently set up a tropical West Africa themed exhibit for a public aquarium, based on similar tanks I have maintained at home and at the Bronx Zoo.  It was a big hit and generated many inquiries from visitors who wished to have a similar aquarium in their homes. 

The aquarium I’ll describe here is similar to that exhibit.  It houses animals from the same region of Africa, and includes two of the pet trade’s most interesting and overlooked fishes, a social shrimp and an active, aquatic frog.  All follow different lifestyles and utilize unusual feeding methods, yet they co-exist very well.

General Considerations

The animals described below hail from West Africa, and all prefer heavily planted aquariums maintained at 78-80 F.  They are quite sensitive to water quality, so be sure to choose a filter that is of an appropriate size for your aquarium, but avoid strong currents (from the filter’s outflow) within the tank.  A comprehensive water test kit  should be used regularly to assure that pH is held between 6.8 and 7, and that the water is moderately soft (water softness is not a major concern, but is best monitored).

Due to the feeding habits of the elephant nose (see below) and the desirability of establishing a lush growth of plants, I suggest that you use Porous Clay Gravel as a substrate.

Peter’s Elephant Nose or Elephant-Nosed Fish, Gnathonemus petersi

This first recommended member of the aquarium is truly interesting in appearance and behavior.  It uses the greatly extended lower jaw from which its common name is drawn to root in the substrate for aquatic worms and insects, its main food source.  Organs near the tail discharge electrical impulses that allow the elephant nose to navigate, hunt and, according to recent research, to communicate (please see the article referenced below).

Feeding and Observing the Elephant Nose

The elephant nose is a confirmed live food specialist, and rarely feeds before nightfall…hence it is always out-competed for food when kept with swordtails, platys and other typical community fishes.  A heavy growth of live plants will encourage it to move about by day; Moonlight Bulbs  are great for use in observing nocturnal behavior. 

Although only small specimens are usually seen in the trade (adults do not ship well at all), the elephant nose can reach 10 inches in length – a group of adults foraging in a large aquarium is a very impressive sight.  Live blackworms can form the foundation of their diet, but you should endeavor to include live bloodworms, glassworms and other such invertebrates regularly.

Click: A Community Aquarium for Fishes, Shrimp and Frogs – West African Oddities – Part 2, to read the rest of this article.

Frank Indiviglio.

Hello, Frank Indiviglio here.

With their ridiculously long “noses” (actually an extended jaw), secretive ways and unique feeding strategies, the elephant-nosed fishes have long been aquarium favorites.  All of the 200+ species discharge electrical pulses from specially-modified muscle cells near the tail. 

The most commonly kept species, Peter’s elephant nose, has been shown to vary the strength, frequency and duration of these discharges.  Doing so helps this nocturnal fish to navigate and hunt in the turbid West African rivers it inhabits.

Using Electricity to Choose a Mate

Recently, researchers at Germany’s Potsdam University have shown that a related species, Campylomormyrus compressirostris, identifies potential mates by the characteristics of their electrical discharges. 

In laboratory tests, gravid females responded to the signals of males of their own species, but ignored those of a closely related fish that shares their natural habitat.  In this way, they are able to locate a mate of the proper species, even when surrounded by similar fishes in murky water at night.

It is theorized that Peter’s elephant nose also uses electricity as a form of communication and mate recognition.  Certainly, watching them avoid obstacles and locate buried blackworms in an aquarium at night, it is easy to see how completely they rely upon their electric-generating system.

Keeping Elephant-Nosed Fishes

Although very popular, elephant-nosed fishes require special care and rarely do well in community aquariums.  I recently set up an exhibit housing a group along with some other of their interesting West African neighbors – butterfly fishes, giant filter-feeding shrimp and dwarf clawed frogs.  Please look for an article on this exhibit and their general care soon.

Please Note:  The “trunk-less” fish pictured with the elephant noses is not the victim of an unfortunate accident but rather a related species, the baby whale or stoneroller, Pollimyrus isidori.  They are also quite interesting and do, if you have an active imagination, somewhat resemble (very!) small whales.  I’ll address them in the article mentioned above.

Further Reading

Belgium’s Africamuseum has posted an interesting article on the Peter’s elephant nose (Note: the photo appears to be of a deceased fish…they are much more attractive than pictured here!): http://www.africamuseum.be/museum/treasures/gnathonemus%20petersii

Please write in with your comments and questions.  Thanks, until next time, Frank Indiviglio.