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Guide to killi-keeping:

Chromaphyosemion bitaeniatum male


A walk into your Local Fish Shop (LFS) will reveal tanks upon tanks of livebearers, cichlids, tetras, catfish, goldfish, anabantoids even many oddball fish like fire eels or snakeheads but sadly very few species of killifish. This gives rise to the impression that killifish are somehow difficult to keep and breed, this is in fact far from the truth.

Unlike the vast majority of aquarium fish they are adapted to live in very small bodies of water which makes them ideal to keep in fish tanks even small ones. They are generally quite hardy and happy to breed in a wider range of conditions than other groups of fish.

Rather than having large clutches of eggs, most killifish species produce a steady stream of eggs over their lifetime. This allows the breeder to adapt their techniques without catastrophic losses of all their fry. It also means they don't have to suddenly house large numbers of fish or have lots of empty tanks waiting for fry to grow out. This is also the reason behind the lack of killifish in the LFS. Because of their steady breeding habits they are difficult to culture in the huge numbers on fish farms to make them commercially viable and few species reach the LFS via this source.

One great advantage killifish have over other groups of fish is that their eggs are hardy enough to post even internationally in a jiffy bag on sealed damp peat or coir. This means a wide range of species are available to you with just a little research online. It also means when your fish are successful at producing eggs you have a large potential customer base you can sell them to. This is obviously not the case for most other fish groups that need to be posting as live fish.

Newly hatched fry of starter species are often quite large and can thrive at room temperature in small pots on a shelf without the need for heaters or filtration.

Killifish can broadly be divided into 2 types depending on their mechanism of breeding - annual and non-annual. Annual killifish are specially adapted for seasonal rains. They lay their eggs into the substrate and require a dry period to continue their life cycle. Annual killifish live life in the fast lane, growing fast and breeding fervently before the pond dries up. Even in an aquarium they grow old quickly and rarely live for more than a year. Non-annual killifish by comparison take it easy, they aren't necessarily short lived in the home aquarium, living to an expected age comparable to other similar sized fishes (perhaps 2-4 years).

Rule number 1 for killifish keeping has to be to use a tight fitting lid on all tanks/containers. Most killies are adept escape artists and every killie keeper has a sad tale of a prize pair of killies being broken up by this miss-hap. You have been warned learn the lesson quickly. Thankfully it is an issue easily resolved with sellotape and cut plastic.

With literally 1000s of species to choose from killifish culture can be an interest to last a lifetime. The real joy in keeping killifish is the breeding and raising of fish and killifish are a great group for home fish culture.

Feeding Adults

White worms, grindal worms, daphnia, bloodworms, tubifex, mosquito larvae, flightless fruit fly, frozen or freeze-dried foods, and good quality fish flakes/pellets are all happily taken by the adults. A varied diet is always good and live foods are needed to condition the fish for breeding. Worms for some reason really stimulate egg production. It is worth joining the "live food cultures for aquariums" Facebook group.

Choosing breeding fish

You will often find you get more eggs from a single pair of fish than a trio (male + 2 females), reverse-trio (2 males and 1 female) or a group. There maybe 2 reasons for this. The simple dynamic of having more fish in the tank means territories are not established and the fish spend less time laying eggs and more time courting/chasing and fighting, i.e. establishing a territory. It could also be that the eggs are being eaten by the none-breeding fish. For an averaged sized adult pair you need a tank or plastic shoe box container of ~ 15L or more. Males are usually very territorial to both other males and to females. Having some good hiding places for the female is extremely important to keep her healthy and unstressed. I find using leaves a great help here. Not only do they replicate their natural environment but females can easily slip away from an overly amorous male. You could add more mops to achieve the same thing however this does make hunting for eggs more of a chore. I also add bog wood, clay pots and floating/sinking tubes. Unlike cichlids or catfish, killifish aren't especially fond of going into tubes and pots but they will happily lay next to them.


Use acrylic wool, not real wool, as it will rot quickly and foul the tank. Colour doesn't seem too important. You may find some colours are easier for you to see the eggs in. Smaller mops are perhaps better as large ones can become difficult to manipulate when harvesting and wet. Try to keep mops clean. After 2-3 months when they start to smell (a) Fish won't lay eggs in them and (b) any eggs that are laid are more likely to go mouldy. At this stage wash the mop thoroughly in very hot tap water the clourine and heat will help to decontaminate the mops. This should be good enough to refeshen up the mops for re-use. Using very hot tap water will also kill any unfound eggs so you can use the mop again with a different species if needed.


Whilst having a well or using rainwater maybe ideal. Many of us don't have this luxury. Also using rainwater can be more variable than tap water over the course of a year, especially if leaves and other debris can get into the water butt. Many commoner killifish aren't that fussy and clean treated tap water will often suffice if all other elements are optimal. My theory is if you get 90% of conditions right for your fish they are likely to breed. If they are healthy, in an appropriate temperature well fed with clean water, conditions such as hardness, pH etc.. which are much much harder to control can be ignored (to a degree) and there are obviously exceptions to this on a species to species level. J.J.Scheel for example in his book "Atlas of Killifishes of the old world" talks about harder/alkaline water being quite good for West African killifish despite the fact that naturally their water would be soft and acidic. The harder water conditions whilst not natural for the killish helped to prevent velvet outbreaks and so the fish were healthier.


One of the great advantages of keeping killifish is that generally they are extremely tolerant with regard to temperature. This stems from the fact that they originate in small bodies of water where temperature can fluctuate daily. Also under the rainforest canopy very little sunlight if any will reach the water to raise its temperature. Temperature can be raised to help stimulate breeding but ambient temperature is usually ok to maintain health for both adults and fry.


Whilst in the wild many of the killifish you will be keeping are from small dark pools under leaves or crevices in rainforests and rarely see the light. There are many advantages of using lights.

  1. You can keep plants with your fish that will help to keep the water clean of nitrates/ammonia and reduce the need for water changes.
  2. You can watch your pride and joys, enjoy their behaviour
  3. You can spot when their are any issues e.g. a female that is getting too much male attention.

Killifish are usually quick to get accustomed to the light, depending on the species. LED light strips are today easy to use and setup. Use a timer or even better a smartimer.


Plants are great to add to fry tubs. Good plants for this include java moss, najas, java fren, duck weed and any other floating plants, hornwort, Hygrophila polysperma, Egeria densa, Elodea etc. Have you tried water cress? Terrestial plants are also great to improve water quality useful terrestrial plants might be - Pothos (very easy), Sweet potato, lucky bamboo.


Leaves are great to add to the breeding setup as they provide an all important refuge for the female. They may also provide some trace elements useful for the fish. I harvest a lot of leaves in the Autumn and keep them for the year ahead as the break down fairly quickly. Leaves I use are Oak with acorn cups, Beech, Hornbeam (acidifying)and Quince.


Snails are you friend in the fry tank (ramshorns, trumpets, bladder snail) they will eat any uneaten food and their poo is easy to see and siphon out with a turkey baster.


Something I like to do in the fry tanks is add some daphnia if I have some either from a small pool or from the pet shop. Baby daphnia can be used as supplemntary food. Larger daphnia will survive in the fry tank for a few weeks and hopefully producing more babies for your fry to feed on.

Sourcing eggs

Get an account on and check society egg lists. Generally you are better off buying eggs in the summer months especially internationally. Be wary of adverts that don't specify the number of eggs being sold and look for sellers that have many buyers. It is impossible to guarantee killifish eggs in the post any cold snap or extended delay is likely to reduce/eliminate viability.

Sourcing fish

Despite everything said in the introduction your first pair of killifish you get are likely to be from an LFS. Many of the better LFS shops will sell killifish if you hunt around. Common killifish found in LFS shops are (Fp. gardneri, Aphyosmeion australe, Golden Wonder (Striped Panchax), Florida flagfish (Jordanella floridae). These are all good starter killifish. Golden Wonders do have large mouths and can be tempted to feed on smaller fish/fry. Something I am keen to do is to keep a varied collection of killifish rather than to specialise in one group. With this it is possible to keep fry from different groups together, you need to be very careful doing this but it does mean you can cut down on the number of fry tanks you have. I often mix fry from Chromaphyosemions with Aphyosemions or Fundulopanchax with a Rivulus type. Make sure you are familiar with the adult females and that they are easily distinguishable, as long as their sizes are comparable they should be happy in a tank together.

Diving for Pearls

Equipment: Light, strong glasses 3.00-5.00 magnification, eye-brow tweezers. It is always a thrill finding eggs. It does take some adjustment to get your eye in. Whilst killifish eggs are usually hard enough to be touched by hand, this is not recommended as our fingers are likely to transfer fungus spores. Eye-brow tweezers curve together at the tip and are great for picking eggs. Hook the egg between the tweezers and gently teaze/ roll the eggs out of the yarn.

Egg incubation

The big problem here is fungus. Fertile eggs shouldn't really fungus unless damaged. However any egg that does fungus can quickly cross-contaminate others healthy eggs. Eggs in a dish in liquid have a tendency to roll together and any fungus eggs will send out filaments that quickly snare healthy eggs. I have a dedicated 1 litre bottle which I add a commercially available solution called fungistop (Tetra) to at 2 drops/litre. I also add a very small amount of salt to this ~1/16 teaspoon to help prevent velvet. I store the eggs in well labelled margarine/take-away tubs. If you do see eggs going white remove them as soon as possible. If you start to have big issues with fungus you should water incubate the eggs over a substrate (I would recommend sterilized coir). The eggs sink into the susbtrate and don't roll together with this method fungussed eggs are physically separated from good quality eggs. The only downside to this is its harder to see the eggs mature. Another mechanism useful for egg incubation is to instead of water incubating is to store on directly onto damp peat/coir. This has several advantages (1) any mouldy eggs can easily be removed (2) You can now easily watch the eggs develop (3) If you add water when all eggs are fully developed you will get an even hatch and the fry will be of an even size which will help reduce fry on fry aggression. (4) Storing the eggs this way is also useful if you want to sell or post them as they are ready to be counted and bagged up.


I would suggest to avoid trying annuals until you are familiar with non-annuals. You may get lucky and find you are a dab-hand with them, but my suspicion is that most annual keepers have been keeping killifish for some time and started on non-annuals. If you do try annuals get the eggs from a reliable source. Someone on Aquabid who apppears to be a popular seller or a BKA/AKA club seller. Unfortunately there are people who will be happy to sell you bags of peat. Whilst this is also true of non-annuals, the fact that you will likely be incubating the eggs yourselves after arrival means any issues to an untrained eye are not immediately apparent. I would also suggest starting on species that have short incubation times (~2 months) and produce large fry. e.g. Nothobranchius guentheri. Watch for eggs eyeing-up before adding water. The eyes look like little golden dots or rings inside the substrate. I would also suggest if anything leaving the eggs slightly longer than the recommended incubation times especially if not storing with some heat. It is very tempting to wet the eggs early when new and keen and you run the risk of having immmature fry i.e. belly-sliders.

Fry Containers

I used to use chinese take-away tubs, I liked the fact they were a free and plentiful source. It is however labour intensive keeping many small containers clean. So perhaps a better option are small 2l plastic containers. Create a hole in the corner of the lid with which to pipette food in. You can also use large open topped glass jars of a similar volume. You may want to add filtration and with the explosion of Nano tank cultures very small sponge filters are now available.

Troubleshooting mouldy eggs

  • Change your incubation method, try using a substrate to reduce the ability of mouldy eggs contaminating any healthy eggs.
  • Clean the tank water, mops, instruments,
  • Harvest the eggs with more care, try using tweezers.
  • Are the fish still quite young? if you can try changing the male that you are using.

Troubleshooting lack of eggs

  • Give the tank a healthy water change.
  • Check the temperature that the fish are at, Do you need to add a heater and increase the temperature?
  • Is the female being bullied? Do she have tattered fins, spend a lot of time hiding, does the male chase her away whenever he sees her? Try a trial separation for a week or two. Add some leaves to the breeding tank to give her plenty of places to find refuge.
  • Perhaps they are laying eggs but in the wrong place? e.g. into plants or into the substrate? Look for mating activity, perhaps provide a substrate.
  • If all else fails start to think about changing other water parameter if you can.
  • Feed with white worms.


Brine Shrimp Hatchery, Brine shrimp sieve, Airline, airline taps - get many and use them liberally, airpump, Glasses 3.00-5.00 magnification, 2 eye-brow tweezers one for picking eggs, one for picking worms. Small paint brushes, Margarine tubs, Acrylic yarn, corks, Fingistop, turkey baster (for fry tank cleaning). Nano tank siphon. Small paint brushes, pippettes, small net.


Labels (small and large) - used to label species names, number of eggs collected, when last cleaned.

Fundulopanchax cinnamomeus male