With their dis­tinc­tive trunk-like snouts and big­ger than av­er­age brains, ele­phant­noses are in­tel­li­gent, un­for­get­table odd­balls.

Practical Fishkeeping (UK) - - Contents - DAVID WOLFENDEN Dave is a for­mer aquat­ics lec­turer and is cu­ra­tor of the Blue Planet aquar­ium in Ch­ester.

With their big­ger-than-av­er­age brains and pe­cu­liar trunk-like snouts, ele­phant­noses are sim­ply un­for­get­table. Oh, and they’re elec­tric too!

WITH THEIR bizarre and un­for­get­table looks, unique be­hav­iour and in­cred­i­ble abil­ity to ‘see’ us­ing elec­tric­ity, the ele­phant­noses truly de­serve their odd­ball sta­tus. While they can make in­cred­i­ble aquar­ium sub­jects, they’re also some­what cryp­tic and de­mand­ing, so you need to put a lot of thought into cater­ing specif­i­cally for their needs.

Ele­phant­noses be­long to the Mormyri­dae fam­ily, which cur­rently con­tains 228 recog­nised species. All come from Africa and are found in a va­ri­ety of fresh­wa­ter habi­tats – in some lo­ca­tions they’re ex­tremely abun­dant. None are found in brack­ish wa­ter as even slight lev­els of salin­ity raise the con­duc­tiv­ity of the wa­ter, af­fect­ing the fish’s elec­trosen­sory abil­i­ties.

The strange ap­pear­ance of the mormyrids gives these species a def­i­nite wow fac­tor, but there is huge di­ver­sity across the group.

When the term ‘ele­phant­nose’ is men­tioned, most fish­keep­ers think of species with a highly move­able, pro­trud­ing snout – the won­der­fully named schnauzenor­gan, used for de­tect­ing food in muddy or sandy sub­strates. The mor­phol­ogy of this ap­pendage varies ac­cord­ing to the pre­dom­i­nant sub­strate type in the species’ habi­tat.

But not all species have a schnauzenor­gan; there are also blunt-nosed species that tend to feed in mid-wa­ter, rather than near the bot­tom, and have more of a dol­phin- or whale-like ap­pear­ance.

Friends elec­tric

Schnauzenor­gan or no, all ele­phant­noses are weakly elec­tric fish. This means they gen­er­ate an elec­tric cur­rent from an or­gan in their cau­dal pe­dun­cle – es­sen­tially highly mod­i­fied mus­cle tis­sue.

Mormyrids gen­er­ate pulses of elec­tric­ity – typ­i­cally 20 pulses per minute at rest, as op­posed to the con­stant waves pro­duced by South Amer­i­can knife­fish, al­though the gen­eral prin­ci­ple is sim­i­lar.

The head, plus the dor­sal and ven­tral parts of the fish’s body, are cov­ered in very sen­si­tive elec­trore­cep­tors that can de­tect the elec­tric field gen­er­ated, which is known as the elec­tric or­gan dis­charge (EOD). Ob­jects en­ter­ing the EOD field create dis­tor­tions that the mormyrid can de­tect and in­ter­pret, and the de­gree of dis­tor­tion varies de­pend­ing on whether the ob­ject is in­or­ganic

With their bizarre looks, unique be­hav­iour and in­cred­i­ble abil­ity to ‘see’ us­ing elec­tric­ity, the ele­phant­noses truly de­serve their odd­ball sta­tus

(a rock, for ex­am­ple), or or­ganic (such as a preda­tor or prey).

The EOD is an amaz­ing adap­ta­tion to a noc­tur­nal life­style in tur­bid wa­ter and is used for nav­i­ga­tion, for­ag­ing and com­mu­ni­ca­tion. Us­ing the EOD, mormyrids ap­pear to be able to dis­tin­guish be­tween dif­fer­ent ma­te­ri­als in the wa­ter, and even whether prey is alive or dead. EODS are species-spe­cific, and also vary be­tween male and fe­males of the same species, play­ing a cru­cial role in courtship be­hav­iour.

Mormyrids are in­tel­li­gent fish, hav­ing pro­por­tion­ally large brains and a well-de­vel­oped and spe­cialised cere­bel­lum with a tightly folded por­tion known as the valvula cere­belli. The con­vo­luted, rib­bon-like mor­phol­ogy of this part of the brain gives it the huge sur­face area needed to process the highly com­plex in­for­ma­tion the fish at­tains from the EOD. Un­ravel the valvula cere­belli of a mormyrid, and it’ll stretch to over 10 times the body length of the fish it­self.

Wa­ter pa­ram­e­ters

Mormyrids are sen­si­tive to changes in wa­ter chem­istry, so pro­vide sta­ble con­di­tions – a ma­ture, fully cy­cled sys­tem is a must.

They will need a tem­per­a­ture of 24-28°C, with zero am­mo­nia and ni­trite. Aim to main­tain ni­trate as low as pos­si­ble, too. Medium hard­ness and a ph of 6.0-7.5 suits them fine. Treat wa­ter with a con­di­tioner, and ide­ally age the wa­ter by aer­at­ing and pre-heat­ing it over sev­eral days be­fore per­form­ing wa­ter changes.

Mormyrids have been shown to have ex­cep­tion­ally high oxy­gen de­mands (nec­es­sary to main­tain their huge brains) so you need to en­sure ad­e­quate turnover and aer­a­tion to main­tain oxy­gen as near sat­u­ra­tion lev­els as pos­si­ble.

Choos­ing & quar­an­tin­ing

When buy­ing mormyrids, se­lect your spec­i­mens very care­fully. Ele­phant­noses can suf­fer dam­age or be gen­er­ally stressed by ship­ping, so you need to closely in­spect them in the flesh. En­sure they’ve set­tled

in at the dealer’s, and look for full-bod­ied in­di­vid­u­als with no signs of ema­ci­a­tion. Ask to see them eat­ing if pos­si­ble – a good mormyrid should be ac­tively for­ag­ing and greedily feed­ing.

Ele­phant­noses are of­ten im­ported with in­ter­nal and/or ex­ter­nal par­a­sites, so quar­an­tin­ing new spec­i­mens is highly rec­om­mended. The quar­an­tine tank can be kept quite dark, al­low­ing the fish to set­tle in and adapt to cap­tive di­ets be­fore be­ing moved to the main aquar­ium.

Mormyrids are scale­less fish, so they are very sen­si­tive to med­i­ca­tions. Most of the com­mon treat­ments that might safely be given to other fish are a no-no, in­clud­ing cop­per and for­ma­lin. Even salt will cause is­sues, al­though praz­i­quan­tel ap­pears to be safe if treat­ment for flukes is re­quired.

In gen­eral, rest­ing the fish with min­i­mal dis­tur­bance, en­sur­ing that they feed in the first few weeks, and main­tain­ing op­ti­mal wa­ter qual­ity is the best way to get them in good health. For the quar­an­tine sys­tem, you’ll need a pre-ma­tured fil­ter and be pre­pared to per­form small, fre­quent wa­ter changes.

Sub­strates are of­ten omit­ted in quar­an­tine sys­tems on hy­giene grounds, but with ele­phant­noses it’s es­sen­tial to in­clude one.

Ele­phant house

Ele­phant­noses need a set-up that caters for their par­tic­u­lar and ex­act­ing re­quire­ments. They don’t fare well as an af­ter­thought ad­di­tion to a com­mu­nity tank, and now that aquar­ists and re­spon­si­ble stores have wised up to this fact, they are thank­fully not of­fered for sale as fre­quently as they were a few years ago.

Mormyrids need larger tanks than many peo­ple think. The most com­monly of­fered species,

Gnathone­mus pe­ter­sii, needs at least a 2m-long tank for a group of five or so, slightly less for an sin­gle spec­i­men. Over­all vol­ume is less im­por­tant than area, and the big­ger the bet­ter – these are def­i­nitely not fish for a nano tank.

They’ve been known to jump when star­tled, so a cov­er­glass, lid or hood is a wise pre­cau­tion.

Be­ing noc­tur­nally ac­tive and well-adapted to murky wa­ter, mormyrids may be­come stressed in gin-clear, brightly lit aquar­i­ums if they’re un­able to hide, so pro­vide

plenty of cover and dimly-lit ar­eas. Sta­ble rock caves are a good ad­di­tion and can be safely built around pieces of PVC tube for a dis­creet, nat­u­ral look.

Soft, fine sand in which the mormyrid can search for food is an ab­so­lute must. Too of­ten, ele­phant­noses are placed in sys­tems with coarse gravel, which is to­tally un­suit­able. Large, rough-grained sub­strates can dam­age the sen­si­tive snout and make it dif­fi­cult for the ele­phant­nose to forage. Add some smooth cob­bles and wood to help the fish feel at home.

Thought­ful plant­ing can add vis­ual in­ter­est and pro­vide ex­cel­lent cover for mormyrids, al­though the bright light­ing you need for some plants may cause the fish to hide, so you’ll need to strike a bal­ance.

A planted sys­tem suit­able for mormyrids could have fo­cused spots of plant-rich zones, with other ar­eas left rel­a­tively dimly lit. Suit­able African plants in­clude Anu­bias species, which can be placed in the sub­strate or at­tached to wood, and African wa­ter fern, Bol­bitis heude­lotti, which needs to be placed on rocks or tied to wood.

Feed­ing mormyrids

The largest mormyrid species are preda­tory, but those of­fered in the trade tend to­wards smaller prey such as lar­val and adult in­sects, plus small snails and crus­taceans. That large brain re­quires a lot of fuel, and mormyrids can rapidly lose con­di­tion if their feed­ing needs aren’t be­ing met.

A well-fed ele­phant­nose should have a slightly plump ap­pear­ance – if the body isn’t slightly rounded, the fish needs more food, and if the body looks hol­lowed-out, then it’s in real trou­ble.

Ideal foods for mormyrids in­clude blood­worm, tubifex and glass­worm, plus crus­taceans like Daph­nia. These should prefer­ably be live when the fish are newly in­tro­duced to en­cour­age feed­ing, but once set­tled, they will ac­cept frozen and freeze-dried ver­sions (al­though qual­ity live food is best).

Pro­vide as much va­ri­ety as pos­si­ble and ex­per­i­ment to a de­gree, but do keep an eye on the con­di­tion of the fish to make sure they’re re­ceiv­ing ad­e­quate nu­tri­tion.

Im­por­tantly, these fish can’t ef­fi­ciently chew their food, so large pel­lets and meaty chunks won’t cut the mus­tard.

Peters’ ele­phant­nose

Of the 200-plus known mormyrid species, only a hand­ful make it to the aquar­ium trade, and one species makes up by far the vast ma­jor­ity of in­di­vid­u­als im­ported. Peters’ ele­phant­nose, Gnathone­mus pe­ter­sii, comes from the Niger and Congo basins and for most aquar­ists, it’s the quin­tes­sen­tial ele­phant­nose fish.

In terms of looks, G. pe­ter­sii is quite at­trac­tive com­pared to cer­tain other mem­bers of the fam­ily – it’s not ex­actly pretty by any stretch of the imag­i­na­tion, but it has in­ter­est­ing bar-like mark­ings on the pos­te­rior half. It varies from light brown to black in colour, and there’s some­times a sub­tle irides­cence when it catches the light.

The fish’s most ob­vi­ous fea­ture is its prom­i­nent schnauzenor­gan – see one in ac­tion search­ing the sub­strate and you’ll un­der­stand why pro­vid­ing soft sand is so im­por­tant.

G. pe­ter­sii can re­port­edly reach 35cm in length, but most aquar­ium spec­i­mens rarely ex­ceed 25cm. Even so, that’s still a big fish that needs a con­sid­er­able amount of room, es­pe­cially if it’s go­ing to be kept in small groups.

Keep­ing pairs can be prob­lem­at­i­cal as two in­di­vid­u­als may fight in­ces­santly, so aim for five or even more fish if space per­mits. The feel­ing here is that ag­gres­sion is spread out in a group, so no one in­di­vid­ual is tar­geted (much the same way as Malawi cich­lids fare best in densely stocked tanks).

Some aquar­ists sug­gest that while sub-adults may tol­er­ate one an­other, ag­gres­sion and ter­ri­to­ri­al­ity in­creases as the fish reach sex­ual ma­tu­rity. This isn’t al­ways the case, but pro­vid­ing ad­e­quate space and hid­ing places can re­duce any prob­lems.

BE­LOW: G. pe­ter­sii is the most com­mon and most suit­able ele­phant­nose for home aquaria.

BE­LOW: G. schilthuisi, a rare ‘short snout’ type.

LEFT: The Worm-jawed mormyrid grows to 40cm. ABOVE: A shoal of ele­phant­noses turn the sand over while feed­ing.

Ele­phants need cover and ar­easof dark­ness.

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