Least Killifish – Habitat, Care, Feeding, Tank Size, Breeding

A member of the Poeciliidae family, the Least Killifish (also known as dwarf top-minnows or lesser Killifish), may be found in lakes and rivers worldwide. They are not just the world’s smallest livebearer but also one of its tiniest fish species. 

Females are just approximately 1 inch long. Males, on the other hand, maybe the world’s tiniest vertebrates. They are energetic, gregarious, and friendly despite their small size.

They can also quickly adapt to most water types, suitable for individuals with smaller tanks or beginning breeders. Aquarists have cultivated lesser Killifish because of their tolerant temperament and small size. 

Only a few fish will provide you with more chances than the smallest Killifish. So, if you have a soft spot for least Killifish, we’ll go over some crucial characteristics of this fish, such as caring for them.  

Least Killifish Care

The smallest Killifish are mostly found in freshwater. However, this may thrive in brackish settings. 

Least Killifish

The least Killifish is often found in slow-moving rivers or stagnant ponds, surrounded by marginal plants or dense vegetation.

They are found at the weedy borders of plant-filled environments in Alabama’s coastal lowlands and South Pine Hills. Due to their ease of capture, it’s enticing to gather them yourself. 

However, it is essential to adhere to local legislation by getting the required licenses. Additionally, if there are no local limitations, you should have a supply of medication on hand to treat any parasites that may be connected with wild-caught livebearers.

Least Killifish Temperature

Coming from warm and tropical sections of the nation, an optimal temperature for your tank will match the Least Killifish’s subtropical habitat.

Keeping temperatures somewhat warmer than normal is critical to maintaining a more natural environment for this fish. Temperatures between 69 and 79°F (21-26°C) are sufficient.

Least Killifish pH

The acidity of water is always measured in pH. The optimal pH level for this fish is between 7.0 and 8.0. For a homeowner, this is good since most water is found in this form. 

If you want your fish to flourish, you should check the pH of their water often.

Least Killifish Size

Although the Least Killifish is a very tough fish, it is one of the tiniest in the world and the smallest in the United States. With this in mind, you’re not looking at a large fish. Males reach a maximum length of around 0.8 inches, while females reach about 1.2 inches.

Least Killifish Tank Size

The Least Killifish should be maintained in an aquarium tank with a minimum capacity of 5 gallons. Due to their tiny size, they are ideal for micro tanks. Even in such a little tank, with the correct setup and upkeep, the fish may flourish.

Aphyosemion fish Aquarium fish from genus Aphyosemion. Killifish stock pictures, royalty-free photos & images

However, maintain Least Killifish in a smaller aquarium, such as a 2.5-gallon tank. At this scale, maintaining a constant water parameter is quite challenging. 

Additionally, there is insufficient fish to swim, explore, and engage in normal activities. It is advised that Least Killifish be housed in tanks of 10 to 20 gallons in size. 

If you have a lot of fish or want to breed them, you’ll need a large enough aquarium.

As a general guideline, one gallon of water should be provided for every inch of fish in the aquarium. It’s also critical to have a properly operating biological filter in your filtration system.

Least Killifish Food & Diet

At least Killifish need to have a broad diet of both plant and protein-rich foods. A good diet is best for their health, even if they aren’t very picky eaters. It’s particularly important if you want to use them in breeding programs later on.

Kisaki Killifish Nothobranchius flammicomantis Killi aquarium fish

You may feed your Least Killifish a variety of fish food, but quality flake food should be their mainstay. They may also be given daphnia, mosquito larvae, and other tiny invertebrates as live fish food.

Natural algae growth in the tank may be enough to satisfy their plant-based nutritional needs. Algae wafers may be used as a supplement if there aren’t enough algae for the fish to feed.

Least Killifish Lifespan

There is a three-year life span for Least Killifish. A proper tank setup and routine care are essential to the fish’s long-term health.

As a result of lower temperatures, life expectancy may be increased. Their metabolism slows down due to a shorter lifetime.

On the other hand, low temperatures might impair the fish’s immune system, resulting in a shorter lifetime. Therefore, it is critical to maintain the temperature in the acceptable range.  

Least Killifish Tank Mates

Least Killifish are little and calm fish that prefer single-species aquariums. They should not be housed in “community” aquariums with other tiny fish like Endler’s Livebearers and aquatic snails. 

Bear in mind that the fry of the Least Killifish may be devoured by other fish species (but not by their kind).

Least Killifish Tank Setup

With Least Killifish, occupying the top level of the tank will take more time than not since they like jumping. To avoid this, ensure that your tank has a cover.

Additionally, you may add plants on the top for aesthetic purposes. A somewhat undemanding fish, water factors are irrelevant. On the other hand, if you want it just right, go for a tropical planted setting.

Least Killifish Breeding

This fish, like the majority of Poeciliids, is a live-bearing species. It implies that it will store its eggs within until they are mature enough to be born. When a man utilizes his anal fin or gonopodium to carry sperm to a female, this is called insemination.

LYRETAIL KILLIFISH aphyosemion australe, ADULTS

What distinguishes the Least Killifish reproductive strategy is that it does not discharge all of its fries at once but over a two-week or longer period.

Least Killifish Diseases

The good news for owners of the Least Killifish is that it is resistant to a wide variety of diseases.

However, like with any fish, it might grow unwell, necessitating continued care. Skin and Gill Flukes, Tapeworms, Bacterial/Fungal Infections, and Columnarius are all common illnesses to avoid. All of these issues are evident and may be avoided by maintaining a clean tank.

Least Killifish Water Conditions

The least Killifish can live in a wide range of water conditions, as shown above. However, to maintain the fish healthy, you need to ensure that the water environment and conditions are ideal for the Killifish. They will be able to live a longer and happier life in your tank. 

Although they prefer warmer climates, the least Killifish can tolerate a wide range of temperatures and pH levels, making them a very adaptable species. There aren’t many water quality requirements for the Least Killifish.

The tank water’s optimal temperature ranges from 66 to 75 degrees Fahrenheit (18 to 24 degrees Celsius), although it can tolerate water temperatures as high as 90 degrees Fahrenheit.

The optimal pH range for acidity in water is between 7.0 and 8.0. However, this is not the only acceptable range.

Due to the decomposition of plants, the acidity of certain of the waterways in which they dwell might fluctuate. However, a neutral to slightly basic pH is optimal.

Least Killifish Diet and Feeding

Killifish are considered omnivores since they consume a wide variety of things, including other fish and crustaceans. Carnivores, on the other hand, are more likely to consume meat than plant-based diets.

Killifish in an aquarium Macro photograph of a killifish, Nothobranchus guenteri Killifish stock pictures, royalty-free photos & images

Crushed flakes and similar feeds are no problem for the tiniest Killifish. Keep the menu as diverse as possible.

They like eating freshly hatched brine shrimp, daphnia, mosquito larvae, and bloodworms, as well as other similar items. Feeding the flakes is an option, but it is recommended that you continue to give them meaty things.

Common Least Killifish Diseases

Although dwarf livebearers do not seem to be especially prone to disease, a few do occur with significant regularity.

Naturally, like with any living thing, it is susceptible to various ailments, parasites, and infections – these are only the most frequent ones to watch for that seem to cause the most problems.

These include skin and gill flukes, tapeworms, bacterial infections, fungal infections, and Columnaris (Cotton Mouth Disease).

Because least Killifish coexist natively with elassoma species (pygmy sunfish), bluefin killifish, swamp darters, and ghost shrimp, they are excellent candidates for US native tanks or biotope setups.

15 Least Killifish Tank Mates

Dwarf Killifish aren’t fussy eaters, but they’re also not very aggressive eaters, so that they may be easily outcompeted for food or scared by too active tankmates.

Additionally, they thrive in well-planted tanks at room temperature with slow, slightly hard water, so bear this in mind while choosing housemates. Even so, there are plenty of possibilities.

Pygmy Sunfish, Swamp Darter, Bluefinn Killi, Emerald Dwarf Rasboras, Rosy Loach, and Celestial Pearl Danio. White Clouds, Nerite Snails, cheerful Barb, Otocinculus, Pygmy Corydoras, Asian Stone Cat, and Japanese Rice Fish are just some of the creatures you’ll find.

Breeding Least Killifish

Less Killifish have a reputation for being simple to breed. To a certain extent, this is due to reproducing in ideal circumstances, such as temperature and salinity.

The females carry eggs in their bodies because they are livebearers. They randomly produce and expel fry from their body.

Kisaki Killifish Nothobranchius flammicomantis Killi aquarium fish

When it comes to breeding killifish, you don’t have to put in a lot of effort. Perfect tank conditions and male and female Killifish kept together will do the trick. After that, reproduction will happen on its own.

Variants Of Least Killifish

A modest breeding colony of gold least Killifish can set you back more than a few hundred dollars. They have no black markings and resemble white guppies in appearance. Snow-white strains contrast with goldenrod-yellow ones.

Where Can I Find Least Killifish for Sale?

Although the Least Killifish prefers to live at the top of the water column, it will occupy any aquarium section.

Because it is fearless of jumping, it must be housed in an aquarium with a lid/hood/canopy or, at the very least, a drastically reduced water level. You can easily find out least Killifish from eBay and other stores.

Where Can I Find Least Killifish in the Wild

The Least Killifish may be found in the southern United States from South Carolina to Texas. But if you want to get a glimpse of these little fish, you need to seek slow-flowing freshwater environments.

It’s possible to find ponds and slow-moving streams that are covered in vegetation. The lowlands of the Gulf Coast would be ideal.

In addition to its size and friendly nature, the Least Killifish is one of the hardiest fish in the aquarium world. This fish, despite its lack of color, has a wide variety of environmental and feeding tolerances.


I appreciate the time you’ve spent reading this little guide to the Least Killifish. It’s a fascinating livebearer created by the process of superfetation in the least Killifish. It’s common for individuals to admire their dark skin, particularly the black line and visible stripes.

These fish are often friendlier, less demanding, and withstand tough circumstances, making them ideal for aquariums. These fish are so little means that beginners and experts alike may benefit much from keeping them. A 10-gallon tank has more space for a tiny colony to live in comfortably.


Can Least Killifish be kept alone?

Both the Golden Wonder Killie (Aplocheilus lineatus), a popular and often available killifish, and the Blue Gularis (Fundulopanchax sjoestedti), one of the biggest and most well-known Killifish, may be hostile and should be maintained alone or in groups with other “spirited” fish.

Will killifish kill each other?

Indeed, they can. It arises from a life cycle in which survival of the fittest is the only option. Because they are not schooling fish, they likely harass one another and establish a dominating structure.

How many Killifish can you have together?

Because Killifish are not schooling fish, they may be maintained alone if necessary. However, they prefer to be surrounded by members of their species, both for companionship and because, in nature, safety is found in numbers. As a result, it is advised that you purchase at least three or four Killifish and keep them in a group.

Where Can I Find Least Killifish in the Wild?

Like the Rusty Cichlids, Least Killifish may be found on a variety of internet retailers. For those who don’t want to pay money on a third-party site, eBay is an option. However, there is the American Killifish Association (aka.org), better known as the AKA. This group specializes in Killifish, so it’s a good place to start.

About the author

I'm Gulshan, a passionate pet enthusiast. Dive into my world where I share tips, stories, and snapshots of my animal adventures. Here, pets are more than just animals; they're heartbeats that enrich our lives. Join our journey!