Here we have yet another fish with a name many people are slightly wary of! Between Knifefish, Convicts, and Terrors, anyone not familiar with the hobby might think being an aquarist was a dangerous pastime indeed.
But the Killifish (Cyprinodontidae family) isn’t a threat to anyone. The name harks back to the Dutch term ‘killi,’ which relates to where this little fish is happiest in the wild. In low lying, slow-moving streams and ditches with ample shade.
Killifish belong to the Cyprinodontidage family of freshwater fish who are vibrantly colored, lay eggs, and have some quirky characteristics we’ll get into more detail about later.
These good-natured fish are native to Africa, Asia, and Southern Europe originally but can now also be found in the Americas. In fact, they can be found just about anywhere on the planet except for Australia and the poles.
They make a great option for a single species tank setup, and there is a large variety of species that fall under the umbrella term Killifish. There are over 1250 species that fall into one of 10 groups.
With so many types, we’ll talk about the most popular types found in the trade and some general characteristics that apply to them.
Killifish Behavior
Killifish are well-behaved and make great additions to community tanks, but there are a few rules of thumb.
Males can be aggressive towards other males. So if you want a group, try having one male-only and then any number of females. You can keep all females only as another option.
If you want a breeding pair or are a beginner, keep them in their own tank for added safety.
They are safe to house with other smaller or like-sized fish and will happily get along with tank mates that suit these criteria that are peaceful also.
A very notable point to make here is that these fish love to jump, and it’s not a question of if they will jump, it’s when.
Like little David Lee Roth’s, these fish will go ahead and jump at every opportunity, so avoid any headaches and heartache and ensure you have a secure lid without any large gaps or holes in it. If they could wear spandex and a headband, they probably would!
They also love to school in the wild, so if you can keep a group of females and a single male, you should. Not only with they be happier and healthier, but they will also look stunning.
Killifish like to prowl around the bottom layers of the tank and are quite agile swimmers, and can be known to dart around the tank when it suits them.
Killifish Lifespan
Killies varieties are vast, but there are two types in general when it comes to the life cycle.
There are Annual Killies who live for mere months, but the more typical lifespan for hobbyist varieties is in the range of 2 – 5 years.
In the wild, these fish can survive in extremely dry conditions that shorten their lives as the freshwater streams dry out seasonally.
We will discuss more on tank requirements a little later in this article.
Killifish Appearance
For such a small freshwater fish, Killifish pack a punch when it comes to brilliant coloring that is sharply defined, multi-hued, and with iridescence to spare.
In terms of size, the largest Killifish species can reach up to 6 inches in length, but the more commonly traded species for the hobby are anywhere from 1 – 3 inches.
They have a long torpedo shape with a pointed mouth that is upturned, suitable for snagging insects from the water surface. They have flattened head shapes and lighter underbellies.
Their dorsal and anal fins start further back than classic fish placement, and these two fins are also noticeably larger than the other fins. Their caudal fins are lightly rounded, reminiscent of Mollies.
Males are typically brighter than females, as is so often the case.
Color patterns are typically dotted, and these spots can vary wildly onto a silvery body base.
Some of the most popular types of Killifish to look out for in the trade are:
- Golden Wonder Killifish
- Pearl Killifish
- Red Killifish
- Rainbow Killifish
- Gardneri Killifish
- Clown Killifish
- Lyretail Killifish
- Neon Striped Lampeye Killifish
- Bluefin Not
- Blackfin Pearlfish
- Lyretail Panchax
- American Flagfish
- Blue Gularis
- Striped Panchax
- Striatum Killifish
Killifish Habitat And Tank Requirements
With their smaller sizing for typical trade varieties, you won’t need a huge tank to get into Killies.
Because these fish are found virtually everywhere, they are considered quite hardy, but you will need to investigate specifics for the species you choose. There are a few saltwater species, but the purpose of this article we’ll look at the more commonly used freshwater setup.
These conditions and parameters are just guidelines, so you have an idea of what to look out for, but you should ideally research for anything species-specific that might apply.
Tank Conditions
These fish should be kept in a shallower tank that is around 70% filled to capacity. Did we mention they like to jump? Yes, well, they need room to maneuver to do so without hitting the lid, so this works. Have a domed lid, too; this will help avoid any accidental impact.
Floating plants are what they naturally gravitate to, and you don’t even need a substrate, but most prefer to have a darker type of gravel that will show off their coloring to great effect.
You’ll want to use plants that don’t need a lot of light to thrive, so including things like Java Moss, Java Fern, Anubias, Hornwort, Najas, and African or Indian Ferns will all work nicely.
Driftwood, rocks, and caves are the usual suspects to add interest to your setup. Peat moss can also be added for species that like a lower pH.
Water flow should be negligent, so sponge filters will work best for Killies in your setup.
Water changes will need to be weekly and at least 25% changed over.
Average water conditions are being noted here, but please check your individual species:
- pH of 6.6 – 7.2
- Water hardness – varies, so check depending on the species you choose
- Temperature between 72 – 75ºF (22 – 24ºC)
- Lighting should be on the lower end of the scale as they prefer shaded areas in the wild
Tank Size
The minimum tank size for a pair of Killifish is 20 gallons, and you’ll need to up that size by 5 – 10 gallons for additional pairs you may wish to include.
Choosing a longer tank size is best to encourage active swimming, and water levels can be relatively shallow with a lid. Always remember the lid!
Choosing Tank Mates For Killifish
Fish that aren’t aggressive and are of a similar size works best with Killies.
Some tank mate pairings that really would work well include:
- Rummy Nose Tetras
- Neon Tetras
- Ember Tetras
- Green Tetras
- Danios
- Rasboras
- Small Barbs
- Gourami
- Dwarf Cichlids
- Rainbow Fish
- Smaller catfish species
- Other small peaceful fish
You could also introduce small shrimp species and snails to help keep your tank clean or for added interest.
How To Feed Killifish
Killies are carnivores in general, although a few species will consume some algae.
For the most part, you will be looking at a diet rich in protein that is suitably sized for these smaller fish.
Great ideas to include for their optimum health are larvae, worms, brine shrimp, and other small crustaceans. They like variety and do not tolerate flakes and pellets, so if you’re squeamish about handling live foods, these fish might not be for you!
Foods that are suited for Killifish are things like:
- Brine Shrimp, which they will eat frozen also
- Daphnia
- Mosquito larvae
- Worms
- Paste type foods
- Fruit flies
- Minced beef heart
Common Health Issues Of Killifish
Ich or White Spot Disease is a common affliction for freshwater fish, and Killies are no exception. It is easily distinguished by white spots on the body due to a parasitic infection, and you can often see your fish rubbing on decor or twitching.
Ich is highly contagious and treatable when caught early and suitably medicated. If left untreated, Ich is usually fatal. You will need to treat your fish and the whole tank if you wish to eliminate this freshwater foe.
Fish Lice is another affliction that is actually visible to the naked eye if you look closely. They are often the result of the introduction of new fish or natural elements into the tank and can be a real pain to get rid of.
The whole tank should be treated to kill their eggs, and if you have stubborn ones on your fish, tweezers should do the job, but this should only be done by experienced hobbyists as it’s a delicate process.
A lot of these issues are to do with water conditions or poor nutrition.
Having water testing kits as well as a UV sterilizer will go a long way to assisting you in keeping your fish healthy.
These issues can be minimized with a strict water cleaning and change schedule along with regular checking of your water parameters. Your tank is a living biome, and it may harbor many types of bacteria or parasites that naturally occur but can proliferate to unacceptable levels if the water condition is let go.
How To Breed Killifish
Killifish fall into two camps when it comes to breeding.
You have annual fish who will mate once, complete their life cycle and then die off. Non-annuals will repeat spawn and are the ones who live for multiple years if kept well.
Both types will go through the same process described below; it’s just that the annual fish types mate to ensure survival, but the parents in the wild would die when the riverbed or ditch dries out.
A smaller tank will be needed for a breeding pair with a suitable substrate of sand and peat moss. The female will lay eggs, and once fertilized, she will bury them in the sand so that they are covered completely.
Once the egg burying is complete, remove the parents and be prepared to wait. You’ll have to wait around three months to see the fry hatch and, in the meantime, be patient.
You should remove most of the water to mimic the dry seasonal conditions that they face, but keep it warm and moist. After 90 days or so, you can refill the tank with appropriately warm water in readiness for the fry to hatch.
When you do spot them hatch, they will eat their egg sac, and then you will need to feed them baby brine shrimp or other suitable fry feed for their size.
Are Killifish A Good Idea For Your Aquarium?
Should you take the plunge and have Killifish in your life? We think they’re absolutely worth it.
For a little fish, they certainly provide a rainbow of color without too much worry about fancy water conditions, fancy filtration, or super-sized tank requirements. That makes them an achievable little showstopper for most hobbyists.
And they are so fun to watch because you never know when they might decide to jump in your suitably shallow tank setup. Their lively personalities match their lively appearance.
Just remember that if you’re turned off by feeding live foods, that aspect really isn’t negotiable. Don’t get Killies if you think you’ll resort to trying to get them to survive on pellets or flaked food because they will turn their cute little noses up.
With a huge variety of species to choose from at your disposal, see what your local suppliers have in stock and do some reading up on them to see if they might be right for you.
They’re popular with good reason. There are a lot of Killifish enthusiast groups you can join online, ready to dole out sensible advice.
Take the plunge and go in for the Killie!
