Killifish Overview: Diet, Tank Conditions, And Lifespan


Last updated on September 1st, 2022 at 01:20 am

A killifish is a type of fish that dwells in swamps, ponds, and other habitats. They are also called “freshwater herrings,” but they do not belong to the same family of fish as herring or sardines.

They usually have stripes on their sides and some species take on an orange hue during mating season.

Killifish are sometimes used as a form of bait in the United States, particularly by fishermen who target catfish and sunfish. These fish usually inhabit muddy bottoms where they feed on small crustaceans such as shrimp and crayfish along with various worms and insects that live among the mud.

They also like to eat algae, which explains why they are often found near the surface of the water.

Killifish typically enjoy living in shallow waters with a muddy bottom as well as on or around aquatic plants and submerged logs. They can even be found hiding among the roots of floating plants such as duckweed and cattails.

In stagnant pools, they often swim in tight circles near the surface, while they will usually remain motionless at depths of six feet or more.

They are a successful species that have been preserved due to their versatility and ability to adapt. They can be found all over North America, Europe, Asia as well as parts of Africa. Killifish can be found in bodies of water ranging from large lakes to small ponds.



They are found in the coastal waters of North, Central, and South America. They are also known as mummichog or tinker’s godson. The species can be identified based on their detailed coloration and body shape, but they may not always have a name to accompany them. They can be found in freshwater, brackish, or saltwater and most species are active at night.

The killifish has been recorded as a part of the zooplankton community for over 300 years. It is one of few fish that have thrived after humans began to dominate the planet’s surface area and climate. Despite its extreme resistance to pollution, the killifish is vulnerable to predators and human intervention.

They have a long lifespan of about seven years in the wild but can live up to 12 years when they are well taken care of by humans. They reproduce quickly: females produce between 40-60 eggs at once with about 20% of them surviving.

They also do not need a lot of space and are adaptable to extreme temperatures, which is why they have been able to survive in polluted waters for so long. They feed on crustaceans, worms, insects, and larvae as well as detritus from the ocean floor like leaves or algae.

Cinnamon Clownfish (Amphiprion Melanopus)

Species profile of the killifish


The killifish is a small, shiny creature that lives in saltwater and brackish water habitats such as tidal pools, estuaries, oyster beds, and mangrove swamps. Killies are found on every continent except Antarctica. They have been introduced into many other countries by aquarists or fishermen.

The freshwater variant, the mummichog, is found in coastal areas of North America from New England to Florida and westward into Missouri and Texas. In Australia, they are known as “freshwater herring” or simply “killies”. They can also be called killifish but that name more often refers to members of the family Cyprinodontidae.

Freshwater killies prefer to live in slow-moving or still water with silt, sand, and gravel bottoms that are heavily rooted by vegetation like algae, grasses, and other aquatic plants. They thrive best at a pH range of about six to eight but can tolerate strong variations from 5 up to 11.

Killifish are small and brightly colored, which may serve as a warning to predators of their poisonous nature. The ability of the killie to produce an intensely toxic substance (tetrodotoxin) is attributed largely to symbiotic bacteria living in its intestines that detoxify certain types of food eaten by the fish such as shrimp.

Color and appearance

The killifish is usually a dull yellow, gray, or brown color. They can sometimes be black on the top and white underneath with dark spots all over its body. There are more than 700 species of these fish in Africa, Asia, North America, and South America. These fish come from freshwater streams that only flow during rainy seasons.


The killifish is native to the fresh waters of North America, but they have been introduced in Europe and Asia. They dwell most frequently in pools or streams that are shaded from sunlight by overhanging vegetation. The fish’s habitat also may be close to a stream bank with plants such as watercress, grasses, and other vegetation.

They are often found in the shade of plants that overhang from the water or nearby banks, such as those with tall grasses and aquatic plants like watercress.

Killifish size


Killifish are generally less than two inches long. There is a wide variance in size between species, with some as small as one inch and others up to five inches.

The killifish is a type of fish that has been around since ancient times, with fossils dating back to the Jurassic period over 160 million years ago. The name comes from their ability to reproduce when they are barely more than an inch long and can be found in many places all over the world. They live in bodies of water where there is little or no oxygen.

Golden Wonder Killifish (Aplocheilus lineatus)

Killifish tank size

In a killifish tank, you should provide an aquarium of at least ten gallons. The fish are very small and do not like to be crowded by other large species of fish that may dominate the smaller ones in terms of aggression or territoriality. They can also get lost easily in larger tanks because they have such tiny mouths which means it is hard for them to eat or breathe. If you do not provide an aquarium of at least ten gallons, the fish will most likely die because they cannot survive in such a small space with little food and without enough oxygen.

In order to set up your killifish tank, you may have to clean it thoroughly before adding any water so it is suitable for fish. It also needs to be cycled, or the ammonia and nitrite levels have to decrease before adding any water (or else you risk killing your killifish). This process can take up to a month, so it is important that you wait until then if possible.

The water temperature should stay at about 73 degrees Fahrenheit, and the pH level should be kept at around six to eight. A healthy killifish tank will also have a filter with an air stone or powerhead for aeration purposes as well as water conditioners that lower the chlorine levels in tap water before you add it into your aquarium because this can harm these small fish.

You should also make sure to feed your killifish a lot of food that is low in fat and high in protein. You do not want these fish to become obese, so they need nutritious foods like live daphnia (a type of water flea), tubifex worms, or other small aquatic life such as brine shrimp or bits of krill.

Life cycle

Killifish are most often found living in freshwater ponds, streams, and rivers. They can also live at the bottom of saltwater estuaries for a short time as long they have access to freshwater. Killifish eggs hatch into fry after about three days. Fry typically grow quickly during their first year, reaching sexual maturity by the end of the second year.

Killifish female

The females are usually smaller than males. They also have a much more colorful body during the mating season, which lasts from spring through autumn. These colors can be yellow, red, or blue and they have it displayed on the fins as well as the body of the fish. The skin color changes to match its environment for camouflage purposes so that it is not easily seen by predators.

Balloonfish Facts 'Spiny Porcupinefish'

Killifish eggs

Killifish eggs are typically laid in a nest that is made by the female and can be between 100-1000 killifish eggs. The male will then fertilize the killifish eggs after they have been laid. Killifish fry (baby fish) hatch from their egg within three to five days. They live approximately six months.

Breeding killifish

Killifish are a pretty unique fish in the aquarium hobby for one major reason: they can breed without any outside help. In fact, killies usually take care of their own offspring by carrying them inside their mouths until they’re ready to swim on their own. They use an egg-shaped oocyte that’s developed within its ovary and fertilized in the male’s gonopodium.

The eggs are released into tiny mucus strings with a sticky surface that attaches to plants or other objects at random. When they’re ready, they’ll release their grip and fall to the bottom of your tank for hatching. There can sometimes be as many as 20-30 fries per string.

Are killifish aggressive or peaceful?

Killifish are generally peaceful and not aggressive. They will only attack when they feel threatened or if their territory is invaded by another fish. This typically happens in captivity, as a killifish’s natural environment has plenty of space to roam around wherever it wants to go. However, this doesn’t mean that an individual species can’t be aggressive or territorial.

General care information


What they eat

Killifish are omnivores. They will eat just about anything they can find in the water, including zooplankton and algae as well as more substantial foods like freshwater sponges.

Killifish tank mates

Killifish are a type of fish that can live with many different types of tank mates. Killifish get their name from the German word for “kill,” which is vernacular to describe this species. They are found in particular regions near saltwater, and they look like miniature versions of freshwater tropical fish as well as other marine fish.

Water condition

They are not very sensitive to water conditions, so they can be added with most types of fish without worrying about the tank’s chemistry. They don’t have any special requirements and will easily adapt to a variety of environments. They also do well in community tanks because they tend to stay on the bottom of the tank, and they are also small enough to hide from other predatory fish.

What Is A Goatfish? - 5 Amazing Facts You Should Know

They live in water that has a pH range of between five and eight. The ideal environment is one with soft, acidic water where the temperature can be fluctuating from around 25 to 30 degrees Celsius (77-86 Fahrenheit). They will not thrive when exposed to extremely hard or alkaline waters; furthermore, they are sensitive to fluctuations in water temperature.

Killifish lifespan

The lifespan is around one to three years.

Parasites and diseases

Parasites and diseases are a major cause of their mortality. Some parasites that affect the fish include ichthyobodo, erythrocytozoon, spirorchis, and spironucleus salmonidum which can lead to anemia in the fish. Diseases like viral hemorrhagic septicemia virus (VHS), whirling disease, and fungal infections can also affect the killifish.

Killifishes are one of many species that become a host for ichthyobodo (also known as “white spot”), which is caused by protozoans of the genus Ichthyophthirius. This parasite will result in visible white spots on the fish’s skin and can cause death.

They are host to a parasite known as “white spot” or Ichthyophthirius, which is often fatal when not treated with medication. This disease usually appears white due to mucous that covers the scales of the killi. It has been found to be successful in treating the ichthyobodo by using a combination of salt, potassium permanganate, and water.


They are prey to many predators, including largemouth bass, eels, and other fish. Predators eat them either as adults or fry (babies).

Are killifish hard to keep?

Yes, They are hard to keep.

They require a lot of attention and time in order to thrive. They are sensitive fish that need stable water conditions, so it is recommended to keep them with the species they prefer. It’s also important to have plenty of live plants as well as driftwood or other hiding places for the killifish. If you don’t provide what they need, they may die.

Are killifish cichlids?

They are not cichlids because they do have scales but they don’t lay eggs in the water like most fish species would. They also grow up quickly when they leave their egg and can rapidly change color to camouflage themselves with certain surroundings or predators.