True questions and unshared answers… Hobbyists often ask to themselves questions that already have their good answers, but these answers are not widely dispatched or the good answers fail to prevail because of old beliefs.

With Internet, it is both possible to dispatch the good answers to everybody and to keep these good answers permanently online for newcomers, while a printed article is replaced by another and it is not always easy to access to old articles.

No headline ! The initial author is definitely not an aquarist, but he has the connection with the expert aquarists and the credibility to discuss those true questions with objectivity and poise.

This page is written for standard aquarists to help them separate hard data from fake data and unjustified rumours, to help them develop the right cooperative approach that is prevailing in Killi-Data and among true experienced hobbyists who are members of Killifish associations.

To communicate better, questions are provocatively set and answers are split into past (insufficient or erroneous) answers, present (true, but not always complete) answers, and future answers (the path to a better understanding).

 Name changes : scientific names of fish are changing all the time with no value added and because so called scientists keep quarrelling to end up with a real mess? Past:  names keep changing because there are different schools of thoughts among scientists who are driven by egos, nationalism… the best is to follow the expert of the country where you live.
Present: names do change and this is normal… just a consequence of progress in zoological science and knowledge… and hobbyists have to live with it… any new publication on Killifish bears a progress on our understanding about those very complicated and difficult-to-study fishes… normally any coming publication is peer reviewed and any controversial matter or any opinion-based-only move is not accepted… however, scientists are different (like anybody, like aquarists) and it is not unacceptable that disagreements arise (improvement also derives from positive conflicts, but these disagreements must be evidence-based, not opinion based, and courtesy-based!)… of course, scientists are either "splitters" (who tend to describe many names) and "lumpers" (who tend to accept less numerous names), just like there are more analytic people (who divide, separate) and more synthetic people (who gather)… both attitudes are respectable and none is the best for all cases, permanently… nonetheless, the tools today used by researchers (e.g., sequencing genes, computerized matrixes of characters, detailed morphology, osteology, behaviour) push to a splitting strategy… and you cannot ask a young researcher not to erect new names simply because there are enough : today a genus gathers 5 to 15 species, while in the past it gathered up to 100 species, this is unavoidable… the present situation for Killifish is not a mess at all, far of it : different lists of names are available (Killi-Data book and online, KMI, KFN, DKG), but these lists are very similar (95% of the names are identical) and they tend to harmonize progressively… of course, if you compare names of today with names in your books or journals, published say 10-20 years ago, differences may be huge, but this is not a mirror of a mess, but, instead, of major scientific improvements (and Killi-Data helps you by editing a list of present names, in comparison with the 2 major recent books by SEEGERS AND WILDEKAMP, and also a list of all NAME CHANGES since 2001, and also POCKET KILLI-DATA, a yearly pocket guide with all valid names and aquarium populations and on top of that Killi-Data has prepared for you a list of correspondances of old names vs. current names, HERE !)… if you are a perfect aquarist, you will make your best to use the actual full name of your fish (and again Killi-Data helps you by editing a constantly updated list of valid names, located in the GUEST section)… if you are a standard aquarist who is not interested by scientific issues, you do not need to use the full actual name of your fish, but instead you have to keep in mind the aquarium population of your fish (to avoid risky mixing), e.g. Buenos Aires, and the species name of your fish (that changes very rarely), e.g., nigripinnis… if you are a pragmatic and reasonable aquarist, you may also add the old name behind the new one, when you distribute your fish (e.g., Austrolebias nigripinnis [Cynolebias]- Buenos Aires)… in conclusion, be sure that the issue of quarrelling about names is definitely old-fashioned among present researchers, who to-day simply do not care… issues of cataloguing, of good spellings, of dates and authorships are to-day 99% solved, but the rest -knowledge on phylogeny, on collections, on conservation- is far more difficult and killifish have taught all present researchers how to be, or to become, modest !
Future: there are not more than 50 sytematics researchers on Killifish worldwide and cooperation can be enhanced by courteously distributing manuscripts for comments before submission to publication… Killi-Data list of valid names aims to lead towards a full harmonization, not because of hegemony, but because this is the best base for strengthened cooperation between aquarists and researchers, to speak the same language… if you are not an Internet nut, then you may, instead of registering to Killi-Data online, obtain the current booklet "POCKET KILLI-DATA" from your Killifish Association (most have subscribed and do distribute it for free or against a small charge to cover their printing costs)… to make it straight, your question is relevant and respectable, the answer is practical and easy (2 names per species, as a minimum : population and species names)… and forget about quarrels : name changes are not today as frequent as in the past… just compare with names and trade marks of your "ordinary life" : how many of those, common and fashionable words, say 20 years ago, are now disused ?
 Good permanent names and codes of collections : what do I do if I am not a member of a Killifish Association? Past: it is better to forget all about this stuff that was introduced by specialists to prevent entry for ordinary aquarists.
Present: again, if you use only the species name and the aquarium population, then the risk of any name change is extremely low (not more than 1 or 2 cases per year over 1100+ valid Killifish species) and your names will be nearly permanent… some people add codes that are an additional information to the population name : these codes identify the year and locality of collection by a combination of letters and numbers (e.g., PEG95/2: locality 2 of the 1995 collecting trip in Gabon by Guido Passaro and Wolfgang Eberl), they are welcome and useful but not compulsory and they can be copied with errors (e.g. PEG95/2 into PEG98/5, a very different strain)… in terms of updating, you can trust Killi-Data : it is continuously updated according to science progress, based on published evidence… finally, how many changes can you trace during the last 20 years : very few at the species level, very many at the genus level, hence the idea of not bothering too much with the genus name, if you are not a killifish nut.
Future: if you are a standard aquarist, just remember the stable population and species names ("my Buenos Aires nigripinnis")… but soon, you'll become a killifish nut and a member of a Killifish association and you will exchange eggs and fish with other hobbyists from all around the world… then your involvement will become more passionate and more serious (full name, correctly labelled ; interest in precise populations ; code of population ; focus on knowledge, ecology and conservation) and you will consider as normal to be informed and to apply news in terms of names for your beloved fishes… do not forget that Killifish are extremely difficult to study and that there are very few researchers worldwide and time and money are limited (why not contribute by donating specimens?)… a good scientific name will be the clearest media of communication between 2 aquarists who do not speak the same language.
 Common names : we should stay as hobbyists and only use common names for our exchanges? Past: this is possible, and permanent names can be achieved either through common names or through codes with 3 letters, like CAM for Aphyosemion cameronense … simple and practical.
Present: with 1100+ valid Killifish species and more than 4000 different aquarium populations, with international exchange of fish and eggs, it is simply unachievable… by nature common names use national languages (do you understand the German names based on Prachtkärpfling?) and additional difficulties arise when species names are identical in various genera (e.g. dedicated to persons, like Myers or Roloff, or with the same meaning like marmoratus, or from the same country like, as above, Aphyosemion cameronense or Lacustricola camerunensis!)… codes with 3 letters seemed a good idea in the sixties when the number of names with aquarium strains was limited, but today it is unpractical (it has been tried to use 4 letters instead of 3, but it did not solve the difficulties and it was less easy to remember the codes).
Future: certainly, the next step is to make sure that no sale to the commercial network (wholesalers, local shops) is undertaken without at least the name of the aquarium population (origin) and at best without the full present scientific name… similarly, no commercial import from native countries of Killifish should be finalised without obtaining the precise origin of the strain (secretive strategies by importers during the pre-world war period has led to unbelievable misunderstandings and errors)… this is also the reason why Killi-Data online is entirely free for petfish magazine editors : hopefully they will then use good names and "solid data" !
 New varieties : we must separate hobby from science by having few strains that we cross to obtain upgraded varieties (better colours, extended fins, curious morphs) like for livebearers or Kois? Past: this is possible, this will enhance the competition in contests, with more fun, and this will leave the wild fish where they should stay, i.e. in nature.
Present: this is clearly not advisable : it has been well known since the sixties that killifish hybrids are commonly sterile (notably at the second generation), even if the 2 mixed populations originate from nearby locations and look like each other… this stems from very different genes that were produced during evolution (and induced by major climatic and/or orogenic changes).
Future: on the contrary, a trend is developing among experienced hobbyists to specialize on rare strains and even endangered species, in order to be sure that their grand children may still look at some fantastic beauties among Killifish that are strongly endangered by human industrialization and/or nonsense… and the conservationist behavior also rightly pushes to maintain aquarium strains, because unreasonable attitudes may well result one day in the complete ban of Killifish importation from the wild by legal authorities (not a theoretical threat).
 Community tanks : we should keep our Killifish with commercial fish just for pleasure at home, why more? Past: no killifish can be kept in community aquariums, forget it.
Present: although most Killifish tend to be reclusive in nature (they live in shallow slow moving or stand still waters), i.e. not mixing with the standard fish fauna from rivers, it is an error to believe that they cannot live in community tanks… first, Lampeyes are great in tropical community tanks (a group of 10-20 specimens swimming against the current is magnificent) together with Characoids or Barbs or small shy Apistogramma-like cichlids… second, most other Killifish, except annuals, may be mixed with standard aquarium fish (notably Epiplatys, Aplocheilus, Pachypanchax), provided that these fish are not predators or aggressive or of a much larger size… third, poor swimmers among killifish (notably Aphyosemion, Rivulus) may also be mixed with not very active fish like catfish, Pantodon… the issue of annual Killifish is another story, but their life cycle is so specific that rare people think of bringing them to their living room aquarium (except for old age retirement… of the fish, not of the aquarist !).
Future: beware that once you have poured a female into a community tank among other Killifish females, it is lost for breeding purposes (females are too much similar and misidentifications are frequent)… apart from that caution, why don' t you try to create, instead, a community aquarium only with Killifish that live in the same area : this will be a mirror of reality, because in nature there are often several species, annuals and non annuals, that live together !
 Belly sliders : how to avoid this frustrating problem? Past: we should stick to few strains with strong selection of the best individuals, like in nature, in order to avoid the problem that just correspond to degenerated material.
Present: belly sliders for annuals is rather a problem of the past and too few aquarists are aware of this : just drop an effervescent tablet of oxygen in your fry aquarium when the problem arise, and that's it (a not 100% miracle, though).
Future: this excellent trick, discovered by fellow aquarists from Killifish Associations (e.g., Jorge San Juan of Spain), will not prevent you from patiently gathering your own observations, i.e. those conditions who naturally prevent belly sliding (and from reporting your experience to Killi-Data)… by the way, the problem is not reported in nature, simply because belly sliders would be an ideal prey ! Finally if the problem is not 100% solved, why not experiment new solutions that you imagine ?
 Unbalanced sex ratios : how to solve that triggering problem? Past: change your water chemistry and temperature, and you'll get some success, who knows.
Present: for extremely unbalanced sex-ratios, it is easy to prevent that issue by putting 5 to 10 fry in a small (isolated) aquarium (instead of all the progeny in a single large tank) : this will end up in a ratio of 50/50, or 40/60, or sometimes even 30/70… if this is not enough, proceed to the extreme option of putting only 2 fry per (isolated) aquarium and you'll have a perfect pair in each (mind you, this is not sorcery : sex reversals are routine processes in nature and Killifish -and livebearers- are not a special case, if sex is genetically pre-arranged, which has to be demonstrated !).
Future: this excellent trick, discovered by fellow aquarists from Killifish Associations (e.g., Jim Robinson of Canada), will not prevent you from patiently gathering your own observations in terms of best practices for chemical data and temperature of water (and from reporting your experience to Killi-Data)… and it is not 100% efficient ! Finally if the problem is not 100% solved, why not experiment new solutions that you imagine ?
 Precise aquarium conditions : what are the ideal conditions for each given species? Past: do not bother, apart from few species, all Killifish can thrive into a 2 litre aquarium (half a gallon) with acid water, from birth to death, full stop.
Present: if you were killifish, you would hardly enjoy your entire life in 2 litres of water… clearly separate your processes into 2 kinds : operational (to produce a good and stable aquarium strain with efficiency) and idealistic (to have active, showy fish, in an ecological environment)… within Killi-Data data base, the ideal ecological conditions are given for each species : large-based aquariums with shallow water (oxygen exchange), correct (varying) temperature, physico-chemical data of the natural habitat, etc… apart from rare brackish or marine or hypersaline species, killifish generally live in 2 types of conditions : (1) pure rain water (with a lot of humic contents -black water- or without -white water-), then slightly acid, on sand and (2) pure rain water on silt-clay substrate, then neutral to slightly alkaline (most savannah annuals), a "waterproof" substrate to maintain as long as possible the availability of the water in the pool… pH is then very rarely below 6 or above 7.5, except if the biotope is polluted by men or women themselves !
Future: listen to fellow expert aquarists… they all stress the importance of regular changes of water (say, 30% weekly), no matter of the chemical data of the water, provided that they are not extreme… imagine you are your favorite killifish, would you like rotten smelly waters as a permanent environment ? … and do not be rigid (or sentimental), reclusive biotopes of your killies do suffer huge variations on a year basis and fish are used to cope with them… if you claim you are lazy, then forget about Killifish (in case it is true)… if it is only a claim, then choose larger tanks and add a population of Ostracods (a good food for Killifish) because these Crustaceans help cleaning poor waters.
 Precise incubation time : for annuals, what is the 100% successful incubation time and conditions ? Past: the best incubation time is given by the time during which the pool is usually dry in nature and the peat condition must be like moist "tobacco".
Present: recent scientific data (Bellemans, Costa, Huber, Watters) show that, within a single pond, sympatric species do not have the same incubation pattern (notably, some species are delayed, but then they grow quicker, and finally they "immorally" eat their -smaller- (and more beautiful) congeners ! … and that eggs are spawned on different strates of the niche to allow variation in incubation conditions and in birth rates (intelligent and flexible nature !)… please, do the same : be pragmatic and flexible… it is easy to divide the spawn into several samples with different values in variables of moist, temperature and vacuum (from a standard basis derived from field data of the concerned species, published in the book Killi-Data and also in the Data Base of this website) and you'll soon know what is your own best estimate fitting with your room conditions.
Future: develop your own learning curve and do not behave like a rigid "accountant" (sorry, nothing against accountants) who wants to have the exact data and cannot imagine he may fail while strictly complying with the "good" data… after all, if there is so much variation reported in aquarium literature, this is not because one author, all the more he is famous, is right and all the other authors are wrong, but because Killifish are flexible (they have to, if they want to survive the constraints of their reclusive biotopes… not only the mediated tsunamis or El Niño, but the more species-threatening glacial periods, the last one being only 2500 years old and having lasted many many decades!… or simply the yearly floods which routinely disrupt everything in the Killifish biotope : water chemistry being the least important).
 Useless cooperation : why do I need to cooperate with others ? Past: forget all these idealistic dreams… you'll soon see that you'll only become interesting when you have a rare species or wild stock.
Present: isolation is a wrong game… you'll soon see what cooperation means when you are left with a single male (or female) of your favorite species… cooperation means strength, shared experience and data, and friendship… 
Future: you cannot imagine what is the most important aspect of killifish hobby for experienced breeders… this is friendship… within the local club, within their Killifish association, within a trans-national specialised group, within Killi-Data community, with a foreigner with whom fish or eggs were exchanged, within a conservationist group to achieve the maintenance of an endangered species or population (what a reward !), with a researcher to whom material for study was donated and who brings unheard results about these unbelievably unique fishes !
Future: Good luck !

HOBBYISTS ' ISSUES (related to the contents and use of the website), click on NEXT

Another question ? Then click on the logo below for direct contact

More specific questions related to Killifish and Aquariums?  Then enter the Website with your e-mail, click on ASSOCIATIONS, choose your country and subscribe for membership.

Discover more on Killies? 

  • What are they? INTRODUCTION to Killies
  • Their biotopes and social and sexual behavior? ECO-ETHOLOGY
  • Their color patterns, their morphs and variability? BEAUTIES of Killies
  • The list of all taxa with their current names, compared to previously USED names
  • The huge database with thousands of pages, photos and maps is only accessible to K-D-I association members, after REGISTRATION