Killifish Care 101: Tank Mates, Size, Lifespan & More!

Killifish are some of the most beautiful, and yet highly underrated fishes in the hobby. When people look for fish to add in their home tanks, these nano fishes are often overlooked; and that’s a real waste. Killifishes are not only gorgeous, they’re also hardy and get along with a whole bunch of other community fish! 

So if you’re on the lookout for a little fish good for solo and community tanks, the Killifish is for you.

The table below gives a quick overview on the Killifish profile:

Profile AttributeValue
Care DifficultyEasy-difficult (depending on species)
Lifespan3 months-5 years (depending on species)
DietOmnivorous/Carnivorous
Color(s)Reds, blues, greens, silvers, browns (depending on the species)
Maximum Size4 inches 
Minimum Tank size20 gallons
Tank SetupLots of hiding areas/Dark gravel substrate
TemperamentPeaceful (aggressive when breeding)
FamilyVarious families of order Cyprinodontiformes
CompatibilityCommunity/species-only tank (dependent on species)

Below is our Killifish care guide, continue reading to find out more about its appearance, diet, breeding and more.

Killifish Overview

The name ‘Killifish’ refers to over a thousand different species of fish from the order Cyprinodontiformes. This order consists of different families, however most consist of freshwater fishes with only a few marine species. 

Coming from different families, killifishes expectedly are a very diverse bunch, having their own unique colors, patterns and finnage. These fishes are usually found in fresh or brackish waters of South and North America. They’re not limited to these areas however; many killifish are also reported in Europe, Africa, and Asia (so they’re practically everywhere). 

The term killifish is widely believed to originate from the Dutch word kil, meaning ‘small stream’. Killis are generally peaceful little guys but can have slightly aggressive tendencies when it comes to breeding (all for love). But when they’re not getting in fights because of females, Killis enjoy a happy, active lifestyle. They’re hardy and are known to tolerate a vast range of water parameters. Some Killis are even able to survive for weeks without water. 

While these guys were often overlooked in the past, their popularity as beloved aquarium fish is now on the rise. 

Appearance

The appearances of Killis vary greatly, since there are around a thousand of them. These tiny packages come in a multitude of vibrant colors such as iridescent greens, blues, reds, golds, and even silvers. They are absolutely stunning to look at, with different patterns and fins and whatever else you can imagine. Killis are classified as sexually dimorphic, with males typically more vibrant and showy than the females. The females are often paler and have more subdued coloring than the males, and have smaller dorsal and anal fins. Some common characteristics among Killi species are their slim, torpedo-shaped bodies, and a dorsal fin near its tail end. Here are some of the hardiest and most popular Killis around: 

Clown killifish (Epiplatys annulatus)

Clown killis get their name from looking like they have clown makeup on. Males have very prominent black and yellow stripes, with blue and red tails (clown colors apparently). However, while this is their common colors, there are still variations among Clown killis. 

Orange Australe killifish (Aphyosemion australe)

This killi comes in both the wild-type chocolate brown coloring, and a golden-orange type. Apart from being a beautiful orange, the golden-orange killi also has tiny red spots along its body and is one of the most popular species in the freshwater aquarium scene. 

Gardneri killifish (Fundulopanchax gardneri)

One of the more common killifish, Gardneri killi males have striking blue-green bodies dotted with purple running its length. Its fins are yellow-tipped, giving a beautiful contrast to its body. Certainly, it’s no mystery why they’re such popular killis. 

Blue Gularis killifish (Fundulopanchax sjoestedti)

The Blue Gularis hails from the same genus as the Gardneri killi. If you didn’t find the Gardneri stunning, then maybe the Blue Gularis is more your type. Male Blue Gularis have bright blue backs, and orange on their sides overlain with brown stripes. They also have flowy, streaming tails that’s sure to catch anyone’s eye. 

Golden Wonder killifish (Aplocheilus lineatus) 

The Golden Wonder Killi is one of the most well-known Killis out there. These fish have a bright, shiny gold color with a neon green flank, and bronze back. Killifish also have unique emerald-green eyes, and red-tipped fins.

Killis are technically small fishes, with the majority of species falling just within 1.5-2 inches in length. Some species like the Golden Wonder killifish, can reach up to 4 inches. 

Lifespan

The life expectancy for Killis depends on the species of Killi that you have. In general, many Killi species reach a long enough lifespan of around 5 years. Some species like the  African turquoise killifish however, have notoriously short lives. These unfortunate souls only hang around for around 3-9 months, before saying farewell. Ultimately, what matters is the quality of life you give you killifish in the limited amount of time they have with us. 

Killifish Care

Killifish care can go from being incredibly effortless to surprisingly difficult. Different Killi species have different adaptations and tolerances to environmental conditions. 

Tank Size

Killis can go from sizes of an inch to up to 4 or 6 inches, depending on their species. As a general rule however, you can house a pair of little Killifish in a 20 gallon tank minimum. You can choose to keep Killis in relatively small, species-only tanks or place them in larger community tanks. It must be said however, that larger tanks have many additional benefits to you than smaller ones.

Water Parameters

Killifish are a large group of more than a thousand fish species. As such, these fishes come from different bodies of water in the wild as well. Killifish can either come from ponds and streams from rainforests, or in tropical savannahs; and because of the varying water conditions, Killifish are able to tolerate a wide scope of water conditions and are classified as hardy.

Water Parameters:

  • Temperature: 68°F-75°F 
  • pH level: 6.0-7.0
  • Hardness: 120-160 ppm (softer water is more conducive for breeding)
  • Water flow: None to mild

For filtration, some aquarists use sponge, or hang-on back filters while more seasoned owners prefer to perform weekly water changes. If you do decide to just perform water changes, you must do at least a 10% change weekly. Some Killis prefer water on the cooler end of the spectrum, while some would need a heater. The same principle goes for the pH levels and their preferred water hardness. In the end, it’s best to tailor your water conditions to the specific Killi species that you have. 

Typical Diseases

Unfortunately, there can be plenty of common diseases that plague your Killifish in an aquarium. These  are the usual suspects: Ick, Fin rot, Columnaris, and Dropsy. Most of the time, a fish contracts these ailments due to poor, or suboptimal water quality. 

  • Ick – By far one of the most common fish diseases, Ick is also called white spot disease. From the name itself, the fish develops white spots all over its body caused by a parasite. Some Ick symptoms are: itchy fish, white spots, and appetite loss.
  • Fin rot – fin rot involves the deterioration of fish fins, as if eaten away by something. Fin rot can cause: discolored body, itchy fish, erratic swimming, and appetite loss. 
  • Columnaris – caused by a bacterium that infects Killis on a poor diet, Columnaris presents itself through ulcers, blurry cloud-like tufts on gills, and discolored gills.
  • Dropsy this illness is also called bloat. Dropsy can cause: enlarged abdomen, appetite loss, discolored gills, boils, and sudden surface swimming.  

Thankfully, most of these illnesses are easily preventable, or treated with medication. Before anything else, maintaining proper water temperatures, pH, and keeping it clean for your Killi species is crucial. Filthy, or unideal parameters that frequently fluctuate end up stressing any fish you have, not just Killis. A stressed out fish is a sickly fish, prone to infections. Apart from their water conditions, your Killis can also get sick if you don’t feed them right. Give them a nutritious and balanced diet to keep them happy and healthy. 

Tank Setup

Because there are so many species of Killifish, it’s best to take this section as a guiding hand and not a strict set of requirements. Research on your specific species of Killifish to create a true paradise for them. The good news is, Killifish have adapted to living in varied environments, so they aren’t too fussy with whatever you place in your tank. In fact, many Killis don’t mind a bare tank, with almost nothing in it. 

Generally, Killis love a couple of hiding places in their homes. Give them some driftwood, cave-like structures and sprinkle on some plants. A couple of good choices are: Java ferns, Java moss, Anubias, Najas, and Cryptocorynes. Killis are also partial to a dim or low-lit environment, so you can’t go wrong with adding floating plants. This not only adds vegetation, but also provides shade to your tank. While a substrate is not really necessary for Killis, you can opt for whatever substrate you like. A dark gravel substrate that mimics their native habitats is a fantastic option. 

Last but certainly not least (possibly the most important), keep your tanks tightly lidded. Killis have gymnastic tendencies so they will jump out of your tank. They’re aquatic little Houdinis who’ll try to escape when they get the chance. 

Food & Diet

In the wild, some Killifish are omnivorous, but most are carnivorous. They devour insect larvae, crustaceans, and the occasional algae. In your home tank, it’s best to try and emulate their love for live food. These little guys absolutely need a high-quality, high-protein diet. To be honest, Killifish don’t take to pellets and flakes very well, so feeding them might be a little inconvenient for some. If you are persistent however, teaching them to eat at least a couple of flakes is still possible. 

Killifish Preferred food includes:

  • Brine shrimp
  • Mysis shrimp
  • Daphnia
  • Mosquito larvae
  • Bloodworms
  • Tubifex worms
  • Black worms
  • Fruit flies

Mating & Breeding Behavior

Killifish can either be annual breeders or non-annual breeders. For anyone interested in breeding these tiny beauties, you’ll be glad to know that it can be easily done. Female Killifish are oviparous, or egg-laying fishes. Firstly, you should Separate your breeding pairs from the rest of the fish community. Breeding males usually become much more beautiful (yup) and more aggressive during this time, while the females remain amiable. 

Fill your breeding tank with some peat moss and sand as the substrate. Your sweet breeding females will typically hide her eggs under the sand. Once these eggs are safely under the sand, immediately remove both the mom and dad, as well as the water in your breeding tank. As an adaptation, Killifish eggs have learned to survive partial dehydration. You have to emulate the dry season by keeping the sand warm and  moist, for around 3 months. Afterwards you can safely place them in water again, where they will hatch into fry. Killifish fry usually just eat their egg sacs for some time, so you don’t need to feed them baby brine shrimp immediately. 

Tip: Male Killis are very aggressive when breeding. To avoid a passion-induced bloodbath, have more than one female for each male in your tank.

Killifish Tank Mates

If you have, or are planning for a community tank, the Killifish would be the perfect addition. In general,  Killifish are amiable and good-natured, and can get along with an array of other fishes. However, there are some males of certain species known to be aggressive towards other Killi males, or even just Killifish lookalikes. To be safe rather than sorry, avoid keeping Killis with fish that look like them. Killi males can oftentimes mistake these poor, innocent souls as possible enemies, and become needlessly aggressive. To avoid any trouble, it’s best to keep Killis with similarly amicable fishes. 

Suitable Tank Mates for Killifish:

  • Neon tetras
  • Dwarf Cichlids
  • Danios
  • Peaceful (small to medium) catfish
  • Gouramis
  • Rasboras
  • Peaceful (small) Barbs
Tip: If you are a certified newbie to the fishkeeping hobby, hold your horses. We suggest taking things slow and just keeping a pair of Killifish alone in a small, species-only tank.

Killifish Temperament & Behavior

As a whole, the Killifish order is a peace-loving, friendly clan of fishes. They’re relatively chill (unless they’re breeding), and easygoing. The males can get a bit territorial and hostile to other males however, so avoid keeping a pair together; if you have no choice, at least decorate your tank with plenty of caves for bullied males to hide in. Apart from these bursts of male aggression, some species of Killifish actually enjoy being in shoals. Certain species become more comfortable and outgoing when in groups (mainly females). 

While mostly laid-back, Killifish surprises many owners when they suddenly jump sky-high in the tank. Indeed, plenty of Killifish have managed to jump out of their tanks and into the floor with their gymnastics. Because of this, you’ll need to tighten security on your maximum security prison-I mean, tank. 

To End

Killifish popularity is growing at a rapid rate for a reason. Depending on the species you choose, Killis can be the nano fish of your dreams. They’re hardy, fun, and gorgeous, all wrapped up in a tiny package! So long as you follow a couple of guidelines and give them the care they deserve, Killifish can make the best aquatic pets.

Note: Please consider the environment before printing this Killifish care sheet.

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