Sport­ing a pal­ette to ri­val any rain­bow, killifish are of­ten nat­u­rally short-lived and tem­per­a­men­tal. But those who em­brace them rarely turn back…

Practical Fishkeeping (UK) - - Contents - WORDS: STEVE BAKER

If you want bright, the world of killifish of­fers a vivid pal­ette with­out the limp credit card or the brain-ache of salt­wa­ter.

IT WOR­RIES me when rel­a­tive novices say “I’m go­ing to start keep­ing marines be­cause the colours are so much brighter”. I imag­ine a lot of spend­ing, and headaches, then nine months on they are sell­ing their whole set-up com­plete with a sur­viv­ing toad­stool co­ral, al­gae­coated live rock and two clown­fish.

Be­yond the stan­dard com­mu­nity tank, fresh­wa­ter fish have more to of­fer than many ap­pre­ci­ate. If you want the chal­lenge then go marine and en­joy it. But if you want bright, the world of killifish of­fers vivid colour with­out the limp credit card or the brain-ache of salt­wa­ter.

Killifish and rel­a­tives in­habit all trop­i­cal con­ti­nents, they have a win­ning for­mula in the wild and with eye-pop­ping colours, mod­est size, cheer­ful char­ac­ter and gen­er­ally af­ford­able price tags, they also have a win­ning for­mula for aquar­i­ums.

So why isn’t your tank full of kil­lis? And why isn’t there an abun­dance of them in shops?

Feed­ing killifish

Killifish are mi­cro­preda­tors, eat­ing small in­sects, lar­vae and crus­taceans. Their diet should be pro­tein and fat heavy. Once set­tled, the com­mon va­ri­eties are easy-go­ing at feed­ing time, al­though it can be a dif­fer­ent story at first. Dur­ing the first two days to a week it’s best to of­fer frozen foods, ide­ally those that stay in the wa­ter col­umn – white mos­quito lar­vae, Daph­nia and brineshrimp.

Re­cently im­ported kil­lies may need sev­eral days of live foods be­fore of­fer­ing frozen. If adult fish are not used to dried foods they may shun them for­ever, so in­tro­duce some as early as pos­si­ble.

Killifish have ei­ther ‘ter­mi­nal’ or ‘su­pe­rior’ mouth types. They are poor at pick­ing food up from the sub­strate so fast-sink­ing foods are of­ten ig­nored. Un­no­ticed food will go to waste – even blood­worm may be over­looked when it’s ly­ing still on the bot­tom of the aquar­ium. So, of­fer mul­ti­ple small feeds a day rather than one larger meal.

Aquar­ium hus­bandry

A ma­jor­ity of killifish in­habit soft and acidic wa­ters, of­ten tan­nin stained and shaded by fo­liage.

Feed­ing raw beef heart will keep killifish strong and colour­ful. Use only good meat, not ‘tube’ bits, and blitz it in a blender

For a rough guide to a biotope we would be look­ing for a dark sub­strate, ide­ally soil based (low-nu­tri­ent shrimp soils work best) with a healthy amount of leaf lit­ter (in­clud­ing bark chip­pings and co­conut fi­bres) and not much else.

Wood can add struc­ture to the tank but I’d lay it flat and build up sub­strate be­hind it for a more nat­u­ral look. With a dark base, leaf lit­ter and stained wa­ter, an elec­tric-blue and scar­let-red fish re­ally stands out.

The main chal­lenge here is main­tain­ing the car­bon­ate hard­ness (KH), es­pe­cially in a small tank. Soft wa­ter plus tan­nic and hu­mic acids cre­ates un­sta­ble con­di­tions so I would aim for around 5°KH up­wards – much lower and ph may fluc­tu­ate eas­ily.

While soft­wa­ter con­di­tions are needed for breed­ing and egg devel­op­ment, many killifish are adapt­able to harder wa­ter con­di­tions. Ex­pe­ri­enced keep­ers of­ten get great re­sults keep­ing them in hard, al­ka­line tap­wa­ter set-ups, mak­ing for a more sta­ble en­vi­ron­ment.

Killifish seem to en­joy clear­wa­ter planted tanks just as much as a leafy biotope set-up – just the kind of bright, clean, colour­ful aquar­ium that many as­pir­ing marine keep­ers are look­ing for.

Posted eggs

With killifish, you can buy ‘dry’ eggs, posted to you by sell­ers and en­thu­si­asts from around the world. By evolv­ing eggs which can be dried (and some­times need to be), killifish have been able to in­habit tem­po­rary bod­ies of wa­ter – and we can use this to our ad­van­tage for ease of trans­port! Hatch­ing the eggs needs only sim­ple equip­ment, like air-driven sponge fil­ters, and can be per­formed in plas­tic tubs rather than glass tanks. Killifish fry are ready to feed straight away, grow quickly, and soon move on to larger and larger foods.

Com­pat­i­bil­ity with oth­ers

Many killifish en­thu­si­asts keep mul­ti­ple small tanks with one species in each, usu­ally with no other tank mates. I’ve kept them this way and en­joyed it – and it also helps to avoid hy­bridi­s­a­tion if you want to breed, but it’s not the only way to keep these lively, de­ter­mined, fish.

Killifish are feisty, bright, fea­ture fish and com­pe­ti­tion with other fea­ture fish won’t end well. Mixed with dwarf ci­ch­lids the killifish will suf­fer; mixed with gup­pies the gup­pies will suf­fer.

Tank mates need to be al­most non­de­script and not too char­ac­ter­ful, and also large enough to avoid the sur­pris­ingly wide mouth of a killifish. For all but the largest species, an adult Neon tetra is safe but young Neons may be snapped up by some larger adult killifish.

An­nual & non-an­nual life­span

Killifish can be split into two groups as far as life­span is con­cerned – an­nual and non-an­nual.

West African Notho­branchius and most South Amer­i­can species, apart from Rivu­lus, are ‘an­nu­als’, mean­ing they in­habit tem­po­rary wa­ter bod­ies that dry up an­nu­ally and so the adults per­ish, leav­ing eggs be­hind them. They are so adapted to this short­ened life that even when kept in an aquar­ium they die young when com­pared to most fish.

Tem­per­a­ture has a large in­flu­ence on a killifish’s ex­act life­span. In

With their vi­brant colours, mod­est size, cheer­ful char­ac­ter and gen­er­ally af­ford­able price tags, killifish have a win­ning for­mula for the aquar­ium

warmer con­di­tions, around 26°C, it may be just six months but keep them cool, around 22°C, and more than 12 months is achiev­able. ‘Non-an­nu­als’ such as Aphyosemion,

Fun­du­lopan­chax and Rivu­lus re­side in more per­ma­nent habi­tats mostly (but not ex­clu­sively and most species’ eggs can be ‘dried’). They have a longer life than the an­nu­als with two or three years be­ing the norm, again be­ing tem­per­a­ture de­pen­dent.

These fish jump!

Be aware of the jump­ing abil­ity of killifish! In the wild they have ad­justed to liv­ing in ex­tremely small habi­tats, some­times just pud­dles where a batch of fry can gen­er­ate high com­pe­ti­tion be­tween them­selves as they reach ma­tu­rity.

Of­ten, less dom­i­nant fish need to move to another body of wa­ter un­der their own power and the only way to do that is by hop­ping and jump­ing across for­est floor. They will also jump out of the wa­ter to catch in­sects above the sur­face, which can re­sult in them ex­it­ing a tank, and end­ing up on the floor. For this rea­son they re­quire a close-fit­ting lid,


The words ‘aphyos’ and ‘semion’ trans­late from Greek into ‘small flag’ (or ban­ner), re­fer­ring to the lyre­tail fins of the males.

This is likely the best genus to keep if you are new to keep­ing killifish.

Aphyosemion species are adapt­able to a range of wa­ter pa­ram­e­ters. They are rel­a­tively ro­bust, easy to breed, non-an­nual fish, full of the usual killifish charisma and the most suit­able to mix with other tank mates. Most of these at­tributes are also shared with Fun­du­lopan­chax.

Habi­tat & dis­tri­bu­tion

Aphyosemion species come from western Africa. Hot spot ar­eas in­clude Gabon, Equa­to­rial Guinea and Cameroon with many species com­ing from this group if coun­tries. They are also found from Togo to Chad in the north, south­ern Demo­cratic Repub­lic of the Congo to the south and ev­ery­where in be­tween these coun­tries.

They live in slow-mov­ing, aged wa­ters in­clud­ing low­land rain­for­est and coastal rain­for­est streams, swamps, pools and river basins. Mostly these habi­tats are soil bot­tomed, shaded by for­est growth and con­tain lots of leaf lit­ter, wood and seed pods. Some species live in sa­van­nah streams with soil and sandy sub­strates; an odd few species live at higher alti­tude in sim­i­lar sit­u­a­tions.

Killifish are feisty, bright, fea­ture fish

be­low: A typ­i­cal killifish habi­tat on the for­est floor.

Above: Small, feisty, colour­ful and del­i­cate.

Line-bred Golden aus­trale males.

Nat­u­ral strain choco­late Aus­trale.

Aphyosemion splen­do­pluere

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