Killifish – Ultimate Care Guide for the Stream Water Fish

Killifish in its natural habitat
By Garrison Hickles Updated

If you love keeping and breeding vibrant and colorful fish in your aquarium because of the hues and appealing activities of your flying-friends act as eye-candy for you, then surely Killifish is the best choice for you. Now, you may ask why Killifish, rather than other species can be your family member. It is very obvious that we like more flamboyant and friendly fish in our fish jar, and Killies have such qualities in them.

Fish-breeders adore them for their multiple colors and cute size. So, why don’t you adopt one of them and add the fish in the family of the other water species in your aquarium? You may also know this American freshwater fish by other names such as Killi, Red-Striped Killifish, Striatum Killifish, and Egg-Laying Topminnow. Moreover, it is comfortable to choose Killies for your fish-tank family if you are a beginner because its less aggressive and more familiar nature appeals fish enthusiast.

Quick Details on Killifish

If you are looking for short details then just have a quick look at this table where you will get to know about Killifish – your new swimmer-companion.

Scientific NameTeleost (Vertebrate Fish)
OriginNorthern America
Life-Span3 months-5 years
ColorRed, Blue, Yellow, Orange, Silver, Brown, Green
TemperamentMost of the Fish are ‘Peaceful’
Size               1-6″( 2-9 cm )
CompatibilityFamiliar to Maximum Water Variants
Tank Size20 Gallons
Care LevelEasy-Difficult (depend on different species)


Killifish comprises over 1250 species and these are categorized with the classification of ten or more groups. They have a very less lifespan about three months to five years. However, the male adult of some species of Killifish survives without water for a week. Generally, Killies are small in size and they can definitely become your calm and friendly companion because of the peace-loving nature. Fish-enthusiasts can purchase Killifish in around £12–16 in shops

Origin of Killifish

You will mainly find Killifish in the shallow sub-tropical freshwater and also in the marine coastal waters of America, tropical countries, Mediterranean countries, and the continents like Antarctica and Australia. Killifish are often found in brackish water and hot springs also. Its common name is Killi because it was first originated in the 17th century with the old Dutch name as a dweller of USA.

At the 20th century, the aquarists started taking interest in catching Killifish and selling them in the market for the passionate fish-enthusiast who like adding collective and new aquatic species in their aquarium.

Killifish Appearance

The vibrant blue, red, yellow and other bright-hued fish are generally preferred by the fish-keepers because of their beautiful appearance and vivid shapes, and you will find the male fish brighter than the female. While talking about their looks and body structure, Killies have flat heads, and the mouths of these fish are at the tip of their face with long teeth set that’s curved and pointed. Commonly, you will find round scales in their bodies with no barbells.

You will often find pike and slender-shaped Killifish, which is the major reason that these fish are active swimmers. However, the shapes and size variates from each other; some have round fins and others have broad fins. The body shape varies depending on the categories. The most common thing is their dorsal fin that is towards the back portion and the males have larger dorsal and anal fins.

These breeds can be both small and large species; small Killies are like the Dwarf Madeka and the Hummingbird Lampeye that are 1-2″ (4-5 cm) long. The larger fish can grow up to 10″ like the Oresteia. Now, you have to decide, which breed you want to keep in your fish tank.

Aquarium Requirements for Killifish

Usually, Killifish in habituated to live in the river and lakes of tropical rainforest that is surrounded by thick forest and natural greenery. So, if you want to see your cute little Killi happy in your fish tank then make the environment and keep the water temperature of their living place as per their requirement and need to be suggested by expert aquarists. You can consider the following suggestions to set a tank for Killifish:

Tank Size

A 20-gallon minimum-sized fish tank is enough for your 6” (15 cm) pet Killifish, but the tank lid should be tight and durable because this aggressive fish has the tendency to jump out from the aquarium. Some small Killifish can be kept in a nano tank or fish jar.


Keep floating plants like Java fern, Java Moss and Anacharis because Killies like to dwell in an eco-friendly environment. Moreover, arrange aquarium caves, fine gravels and sandy substrate for the bottom bed of the aquarium.


Arrange subdued dim light on the top of the fish tank for your pet Killifish because this breed does not like harsh light.


Expert aquarists suggest keeping a small sponge filter that allows gentle airflow and refines the water. Moreover, a good filter will help in killing the bacterial infection in the tank and save your Killies from several health issues.


Usually experienced aquarists use a water heater to maintain the temperature of the water in the winter season. So, if you want to maintain the temperature, you can keep a water heater in your aquarium.


Never use big stones and gravels in the bottom part of the aquarium because some Killies are bottom spawners and the gravels may disrupt its reproduction process. Moreover, don’t add additives and fertilizers in the water which may harm the respiration and consumption process of the fish. You should keep floating plants in the fish tank because Killifish often prefers laying their eggs on the leaves of floating plants; so, they are also known as egg-hanger.

Water Type for Killifish

While setting a tank for your favorite Killifish, look after the temperature, hardness and pH level because, without a suitable water temperature, a Killi cannot survive long. Here are some instructions for you given below:


The temperature of water in the tank of Killifish should be 68-75° F (18-23°C).


The cute little Killifish prefers dwelling in water that’s hardness is between 120 ppm to 160 ppm.

pH Level

The pH of the water should be 6.0 to 7.0.

Cleaning Method

You can use gravel cleaner like Siphon Gravel Cleaner to clean the stones, gravels and other objects in the fish tank. Use liquid soap and a soft brush to clean every portion of the aquarium. After washing out, wipe out the water droplets with a soft cloth.

Replacement Procedure

Try to replace 10% of the water every week and 25% water every month to keep the quality of the water good. During the replacement process, add water conditioner to keep the freshness of the water. Also, check the temperature, pH level, and hardness while putting a new batch of water in the aquarium.

Killifish Temperament

As we have mentioned above, Killifish is peaceful compared to the other fish, so you can easily make it one of the fish family members in your aquarium if you are a starter fish-enthusiast. But it depends on species variation, as male Killies become aggressive when they find same-looking teammates with them, and the female Killifish is quite calm in nature. The peaceful behavior of this fish reduces the risk level of fighting with other fish breeds. Still, your primary task is to find suitable tankmates that have good compatibility with Killifish.

Compatibility and Best Tankmates for Killifish

While planning to keep a Killifish in your aquarium, let’s know about the compatibility and familiarity of the fish because remember, choosing a wrong tankmate for your Killi may result in fights and other problems. Therefore, get an idea from the expert fish-keepers and then choose social playmates for your favorite Killi.

Male to Male Familiarity

Killifish is friendly and peaceful in nature but two male Killies do not prefer staying together, and if you keep them together then the fish may result in indifference and fights. Even they don’t like similar-looking male companions in their home.

Male to Female Familiarity

Male Killies are quite familiar with the female species, so don’t worry while putting them together and making a new friendship between your little fish buddies.

Female to Female Familiarity

Females are not rageful compared to your male Killi friend, so don’t worry, you can easily keep two or more female Killifish together without any doubt.


It is more preferred if you don’t keep many breeds of Killies together like two or three. Try to find more suitable fish species that can live peacefully in a familiar way with Killi. Moreover, you can keep one male and two female Killies together.

Suitable Companions for Killifish

The peaceful temperament of Killifish makes it friendly with any fish species in the tank, but some of them can be the best companions for them such as:

  • Danios
  • Neon Tetras
  • Rummy Nose Tetras
  • Apistos
  • Small Catfish
  • Rasboras

Just avoid keeping male Killies and aggressive species with Killi who can harm your little buddy. Avoid fighting and stress-increasing reasons between your little slimy companions that can be the result of their health issues.

Diet Plans for Killifish

Generally, Killifish is a carnivorous species that prefer eating insects, natural crustaceans and worms but it also likes consuming the green algae in the aquarium. You may observe this breed eating live foods rather than frozen foods, but if the veterinary dieticians and medical experts guide you then you also need to add herbs or frozen eatables in the diet of your little Killi for the wellbeing. The expert aquarists choose these foods while planning the diet of Killifish as follows:

  • Brine Shrimp
  • Insect Larvae
  • Blood Worms
  • Mosquito Larvae
  • Tubifex Worms
  • White Worms
  • Black Worms
  • Fruit Flies
  • Infusoria
  • Vinegar Eels
  • Grindal Worms
  • Micro Worms

You may also buy some frozen and dry foods available for Killifish in the market such as:

  • Beef-Heart Meat Flex
  • Chicken-Egg Yolk Powder
  • Paste Foods
  • Dry Foods
  • Frozen Blood Worm

However, try to feed this fish twice or thrice a day because over-feeding may result in poor digestion and other health problems. So, it is your prime responsibility to ask the expert aquarists about the dying regime of your cute little Killifish for its good health and happy life. Remember, it has a very short lifespan, so you should care Killies properly if you are affectionate to it. Adding much food in the tank can result in toxicity and infection in the tank water that is harmful to the health of every fish in the jar.

Killifish Breeding and Reproduction Process

Killifish get sexually matured in two months and the female species are also known as egg-machine because they can lay 30 eggs in a single day. The reputation of this egg-laying cycle can be observed every three months or once a year. These species are experts in giving birth and sexing, so if you are not ready to collect fish eggs and breed them then don’t keep the female Killies with the males. There are two categories of the reproduction system of Killifish:

Top Egg-Layer

Killifish lay their eggs in the floating leaves, so it is also known as one of the best spawners than others. You just need a bare tank for their breeding process because they spawn high. It is hard to take out the eggs from the plants. It is needed to keep the eggs in the separate small fish tank with minimum temperature water for the fertilization process. These fish require two weeks to get matured and after that, you can hold them with a floating net and keep them with their parents.

Bottom Egg-Layer

The bottom-spawners has high-level sexual maturity from a very early age but less life-span. These Killies are habituated to lay eggs in the peat moss or ground of the fish tank and hide the eggs with the sand. This fish just needs a small tank with peat moss or sand where it can bury eggs. However, if you are planning to encourage the reproduction process of this breed then remove its parents from the aquarium after the eggs are laid and make the water Lukewarm for the fertilization and development process. The development process may need two to three weeks or one month. These types of Killies can live for two years if you care and nourish your little friend properly.

Remember, to follow a natural diet by feeding your new-born Killies of both the categories some necessary eatables that are easily digestible and nourishing such as:

  • Fruit Flies
  • Infusoria
  • Vinegar Eels
  • Grindal Worms
  • Micro Worms

Various Diseases of Killifish with Preventions

Usually, Killies are hardy and adjustable species that can live in any kind of water whether it’s saltwater or freshwater. But it is necessary to look after the health preventions because Killifish has a high tendency to get affected by life-threatening diseases such as:

  • Fluke
  • Cellular Infection
  • Fungal Diseases
  • Bacterial Diseases

So, remember if any fish dies in the water of your aquarium then immediately take the fish out and change the water, otherwise, the dead corpse may be the reason for infectious diseases. These infections will be the source of major health issues that may result in the tragic death of your finned-companion. If you really want a long life for your buddy then look after the dietary requirements, hygiene, environment, and necessary treatments of Killi.

Difficulties in Keeping Killifish

Killifish is a peaceful aquatic species that get easily familiar with other fish, but the male fish are aggressive and they don’t like to adjust with other males and similar-looking species. So, it is difficult to manage their needs, in this case, every time. Moreover, when the bottom-spawners lay eggs on the body of the water or hanging leaves, it is really hard to take out the eggs safely from the plants and breed them safely.

Types of Killifish

As we have mentioned above, Killifish is a big family with 1270 species, among them some fall in the categories of Killies that looks similar to the same temperament. Take a look at a few names:

  1. Lampeye Killifish – This Killifish is originated in central Africa and very small in size. Its lifespan is 3 years and it also has less disease, so fish-enthusiasts love making it their family member.  
  2. Delta Killifish – The mesmerizing look of this Killifish attracts the aquarists and people like to keep it because it’s quite small and easy to care.
  3. Chocolate Lyretail – This West African Killifish also lives in the rainforest, small streams, and ponds. Its lyre-shaped fins and tails help them swim faster than others. If you want to plan its breeding then it is the most clam-natured species that can lay many eggs and fertilize it at a time.
  4. Limeatus – The origin of this Killifish is India, and fish-keepers like it for its vibrant shades and cute size. This is also a typical egg-hanger and easy to breed because these Killies do not need a large-sized fish tank to dwell.
  5. Gardneri – This Africa-originated Killifish has bicolor in its body with yellowtail. It is a sweet-natured fish, generally loved by expert aquarists and easy to keep in the tank for beginners.
  6. Blue Gularis – This is a larger species, hence need much space, but its eggs are easy to collect as it is a bottom egg-layer. These fish are easy to keep and their breeding process is very simple.
  7. Bivittatum – This round-tailed fish lay eggs in floating plants and usually adjustable with all type of water with medium temperature.
  8. Dwarf Argentina Pearl Fish – This Killifish comes from Argentina and its color is appealing with beautiful glitters dorsal fins. Fish-keepers likes to store them because of their color and brightness.
  9. American Flagfish – The American Killifish is interesting in nature because it likes to live with its male sex partner. Its reproduction process is simple as it is one of the bottom-spawners.

Killifish Care Guide

If you are planning to keep a Killifish, just follow the aforesaid instructions and if needed then ask from the fish-keeping experts for the maintenance and well-being process of this breed without any trouble. Moreover, keep these fish with the best companions to avoid their stress-level and isolation which can be the reason of their color-fading. If they are ill and infected then don’t delay to take medical instructions for their treatment. Also, keep them creating a friendly, rejoicing and perfect environment in the fish tank that helps the species stay healthy and happy. Hope the good health of your little friend is your major aim while breeding them.

You don’t need to think much, just keep your little friend like your family member, your child or your sibling. This will help you in taking proper care, safeguards and fulfilling other necessary requirements of Killifish.

Amazing Facts about Killifish

  • Killifish helps in killing the germs and stopping the spread of malaria infection by eating the mosquitos and its larvae.
  • The top egg-layers eat their own eggs, so it is necessary to keep the parents from the eggs immediately after the birth.
  • The Killies have highest sex-drive and fast maturation, compared to other freshwater fish.
  • The bottom-spawners protect their eggs by burring it inside the sand at the bottom of the fish jar.

Know More Freshwater Fish Like Killifish

As a fondling fish-enthusiast, you can also add more new friends in your pet fish family. Have a look at a few of them: