Killifish: Care, Size, Lifespan, Diet & More

Killifish are beautiful and small species of freshwater fish that are known for their beautiful coloration and patterns. There are many different types of Killifish available around the world. Depending on the geological area they live in, they’ve developed unique patterns and beautiful vibrant colors. Killifish are a popular choice for smaller aquariums because they are relatively peaceful and stay small.

These fish have been in the fishkeeping hobby for a long time, but they recently got more attention from aquarists. So we put together this care guide to help aquarists of different skill levels to better understand this species. 

In this article, we will cover the basics and advanced care requirements for this fish and will provide you with many more tips and tricks to give your fish the best life. 

Species Profile & Overview

Killifish are found in most tropical and subtropical regions of the world including North America, Europe, Africa, and Asia. However, the majority of the fish available in the aquarium trade are coming from Southeast Asia. 

Killifish are found in a wide variety of habitats, from slow-flowing rivers to stagnant pools. They are also able to adapt to a wide range of water conditions but prefer waters that are slightly acidic and have a high dissolved oxygen content. 

Their unique features include their ability to tolerate a wide range of water parameters, including being able to live in brackish waters. They also lay their eggs in the mud or dead moss and the eggs can go to aestivate (enter into a state of dormancy) during periods of drought.

Killifish are very active species and will constantly swim around looking for food. They are known to be jumpers, so a tight-fitting lid is a must. Some species of killifish are known to jump more than others but regardless a lid is needed at all times. 

These fish can also be a little nippy towards other fish and may harass slower-moving tankmates. To prevent fin nipping, you should keep them with fish that swim fast. Though it’s best to keep them in schools of their kind. More on this later in this guide.

There are many different types of Killifish in the wild but only the most colorful and colorful variants are kept as pets. These fish are praised for their small size, brightly colored body, and their ease of care. 

Appearance & Types

The killifish is a beautiful fish that is often overlooked in the aquarium hobby. They come in a wide variety of colors and patterns and can make a great addition to any tank.

These fish are small, colorful fish that are popular in the aquarium trade. They have long, slender bodies with large eyes and small mouths. Their fins are often brightly colored, and their pelvic fins are uniquely located far back on their bodies. 

There are many color variations of killifish, and their colors can vary significantly. Some killifish are brightly colored, while others are more subdued. The color of a killifish can depend on many factors, including its environment, diet, and genetics.

There are around 1270 species of killifish known to science. But only a few are available in the aquarium trade. Here are some of the most beautiful types of killifish:

• Clown Killifish (Banded Panchax)
• Blue Notho (Nothobranchius rachovii)
• Redtail Notho (Nothobranchius guentheri)
• Golden Wonder Killifish (Striped panchax)
• Gardneri Killifish (Blue lyretail)
• Blue Gularis Killifish (Fundulopanchax sjoestedti)
• Bluefin Killifish (Lucania goodei)
• Black Pearl Killifish (Austrolebias nigripinnis)
• Lyretail Panchax Killifish (Aphyosemion australe)

Their are many different species of Killifish as well but they mostly lack vibrant colorations and are less likely to be seen for sale in pet stores. Generally, males are more colorful than females and have longer fins than females.

Adult Size

Killifish are small species, usually no more than 2 inches in length. There are some variations in size among different species of killifish, but generally, all species of killifish grow between 1 to 2 inches. 

In terms of body size, there are some outlier species like Cuatro Ojos (Anableps dowel) and Least Killifish (Heterandria formosa). The Cuatro Ojos is a species of killifish that can grow to about 13 inches in length while Least Killifish stays super small at about 8 mm (0.31 in) long as an adult.

Males and females are usually about the same size. In some variants, males may be slightly larger than females but as a general rule, both male and female killifish stay about the same size.

One of the reasons that killifish make such good pets is their size. They are small enough to be kept in a nano, but they are colorful enough to be easily seen and enjoyed. This makes them a great choice for people who don’t have a lot of space for a fish tank and still want to have beautiful fish.

Lifespan

Killifish are small, freshwater fish that typically have a lifespan of 2 to 5 years. However, their actual lifespan inside your tank can be lower or higher. Their lifespan can be affected by several factors, including diet and water quality.

Killis are delicate fish and their lifespan can be affected by genetics, stress, and disease. In the wild, they typically only live for a few years, but in captivity, they can live for up to five years or more. This can only happen if they are properly cared for and live in a stress-free environment.

Behavior & Temperament

Killifish are typically very peaceful fish and get along well with other fish in a tank. However, they can be nippy or even fight with other fish if they feel threatened. This happens in rare cases and not all species of killifish express this behavior.

Keeping a group of Killifish together might not be a good idea if you have a smaller tank or if you want to keep many males together. The males often get aggressive and territorial towards each other and need to be kept in a larger tank that has a lot of hiding spots. 

When kept in a small aquarium, they will become stressed and may become aggressive towards other fish as well. When the aquarium is overcrowded, they may also start to nip on other fish; they often nip at the fins of their tank mates.

To prevent their aggressive behaviors you should focus on keeping a single male in a tank. A single male with a few females will also give you a good school. They will often swim in a school near the top of the tank showing beautiful shoaling behaviors.

Although these fish vary greatly in appearance, they all share some common behaviors. For example, killifish are social creatures that live in schools. They are also good swimmers and can often be seen darting around their tank or pond. 

They also jump out of the water so a lid will be needed to keep them in the aquarium. You can also lower the water level to give them a safe space to practice their instinct. Though your aquarium might not look as beautiful as it is when it’s full of water. 

Killifish Care

Killifish are easy to care for but they are not beginner-friendly fish. This is because they need stable water parameters that most beginner aquarists fail to provide. Despite that, these fish are one of the most adaptable fish around, able to live in a wide range of environments. 

It is important to remember that killifish still need specific conditions to thrive. In particular, their water needs to match the parameters of their natural habitat as closely as possible. This includes things like pH, hardness, and temperature. 

By providing killifish with the right environment, you can help them stay healthy and happy in your aquarium. In the next few sections, we will pave the road for you to start caring for these amazing fish with little to no hesitation.

Tank Size

A killifish fish needs a minimum tank size of 5 gallons. In a 5 gallon tank, you can only keep one small species of killifish. However, we recommend having a 10 gallon tank or larger. In larger tanks, you can keep some company with your killifish and make a better living environment for them.

These fish need to have enough room to swim and to hide when feeling threatened. So a larger aquarium will give them the space they need to be happy and thrive.

What To Put In A Killifish Tank

To decorate the aquarium for Killifish, you can use a variety of different aquascapes. A simple setup with rocks and plants would be ideal, or you could create a more elaborate layout with caves and hiding places. Whichever aquascape you choose, make sure there is plenty of open space for the fish to swim around in.

Killifish are very sensitive to water quality, so it’s important to have a well-filtered and well-aerated tank. They also like to have plenty of hiding places, so live plants or driftwood can be good additions to their tank.

Natural decoration should be your first go-to option as they provide a lot of benefits to the tank and the fish. One of the benefits of using natural decorations like rocks and driftwood in an aquarium is that they help the tank to look more beautiful and natural. 

By using these types of materials, you can create a more realistic environment for your fish that closely resembles their natural habitat. This can provide your fish with a sense of security and comfort, helping them to stay healthy and thrive. 

A good substrate is also beneficial to the tank. The substrate provides a place for the beneficial bacteria to grow while giving the plants a place to root in and under. The best substrate for a Killifish aquarium is sand or fine gravel. These will allow the fish to feel safe and at home while giving your tank a beautiful natural look.

As mentioned, plants are highly recommended for a Killifish aquarium. Live plants can help to create a more balanced and healthy environment for your Killifish. They can also help with oxygenating the water and provide a natural source of food and shelter for your fish. 

But more importantly, plants will absorb excess nutrients (fish waste) from the water, which can help to keep the water cleaner and clearer. This is the main reason we always recommend having fast-growing plants in aquariums.

Some good plants to keep with killifish are Anubias, Buceplants, Java Ferns, and Java moss. All three of these plants are hardy and don’t need much attention from you, making them ideal for a killifish aquarium. You can attach these plants to driftwood or rocks with fishing lines or zip ties. 

If you have experience with keeping plants in a tank then you can go with more sensitive but beautiful types of aquatic plants. Creating a lush jungle in the tank should be your main goal as these fish prefer to live in planted areas. 

Light Requirements

Killifish stays near the surface of the water where light is strong. By doing so, they are defending themselves against the predators in the wild. These fish have a reflective underbelly that makes them somewhat hard to see from below. Basically, under sunlight, they become invisible to the predators swimming below. 

However, in an aquarium environment, they need to live in medium lighting conditions. This is because an aquarium is a small place and fish get stressed if they can’t quickly swim away to hide. This is why these fish often jump out of the fish tank. 

When the tank is fully planted it’s easy for the fish to hide and feel safe. The best type of light for a well-planted aquarium is a full-spectrum LED light. They are more energy efficient and produce less heat than other types of lights. 

The LED aquarium light will often come with the right lumen for plants to grow and the fish to look more beautiful. The reflective scales of killifish will look much more beautiful under a full spectrum LED light than other lights.

Water Conditions & Parameters

Killifish are pretty adaptable species and can survive in a wide range of water parameters. However, like all fish, there is a recommended window that you should aim for if you want them to be as healthy as possible.

The natural habitat of killifish is in freshwater ponds, lakes, and slow-moving rivers. The water in these habitats is typically clean and clear with a moderate pH. The temperature of the water can vary depending on the location but is usually within the subtropical range.

So recreating such an environment is necessary for these fish to thrive. Considering these points, below are the ideal range of parameters for Killifish:

• Temperature: 68 – 75 Degrees Fahrenheit
• pH: 6.0 – 7.0
• TDS: 50 – 150 PPM

It is important to never shock these fish while doing your water changes. Killifish are sensitive to changes in the water parameters so you must keep the tank consistent. A consistent tank is much better than trying to achieve a specific pH or hardness level. 

By changing the water regularly and in small amounts (10% – 20%) you are keeping the water clean while preventing any sudden shift in the tank’s parameters. This will help your fish to live as long as they are meant to. 

Filtration System

Filtration is another key component in keeping the water parameters consistent. A good filter is an important part of keeping killifish healthy and free from disease. The filter will remove debris and waste from the water, making your tank liveable for killifish.

This is especially important in smaller tanks, where there is less water to dilute waste produced by fish. The beneficial bacteria in the filtration system will constantly work to keep the tank clean, making your job of caring for a tank easier. 

The first thing to consider when picking a filter for an aquarium is the size of the tank. A smaller tank will require a smaller filter, while a larger tank will require a bigger filter. The next thing to consider is the type of filter. Killifish need slow-moving water so your filter should not create a fast flow in the tank. 

There are many different types of filters on the market, and they range in price from very affordable to very expensive. It is important to find a filter that fits both the size of the tank and your budget. 

We, however, recommend a simple sponge filter for these fish. Sponge filters will not create a fast flow in the tank and will constantly aerate the tank. They are also very reliable and safe to use.

Diet and Feeding Requirements

Killifishes are carnivorous fish that eat other smaller fish, insects, and invertebrates. They are ambush predators that typically wait near the surface of the water for their prey to swim by before striking. 

While they are carnivores In the wild, in captivity, they will accept a variety of foods, including pellets and flakes. To ensure that your Killifish are getting the best possible nutrition, it is important to feed them a variety of foods. 

A good diet for these species should include both live and frozen foods, as well as high-quality flake or pellet food. Live or frozen foods such as brine shrimp, bloodworms, and daphnia are all excellent choices for Killifishes. 

When feeding live or frozen foods, it is important to offer only as much as the fish will eat in a few minutes. Ideally, these species should be fed 2 – 3 times per day; but that might not be an option for most people with busy schedules. So feed them as much as they eat within a few minutes without leaving any uneaten food in the tank.

Not all dry fish foods are particularly nutritious for the Killifish fish. Most fish foods are made to be budget-friendly and that means they might not have all the nutrients a fish needs. These products are typically filled with fillers and binders such as cornmeal, wheat flour, and soybean meal. 

There may also be small amounts of fish meal or other protein sources, but these are generally not enough to provide the fish with all the nutrients they need. As a result, it is important to supplement the diet of Killifish with live foods or other high-quality sources of nutrition.

Frozen aquarium fish foods are a great way to add variety to your Killifish diet. These foods are affordable and accessible in most pet stores. You can feed your fish a mix of dry and frozen foods daily for the best health and coloration.

As mentioned, never leave any uneaten food in the tank. Overfeeding killifish can cause many health issues for the fish and can easily break the balance inside an aquarium. The waste produced will pollute the water which can lead to an unhealthy environment.

Common Diseases and Prevention

Aquarium diseases can have a significant effect on the health of your killifish. These fish are susceptible to the most common disease seen in the hobby. But the most common disease in these fish is Fluke (monogenean trematodes).

Fluke is a term used by aquarists for a group of flatworm parasites that can attach themselves to the gill and the skin of the fish. These parasitic worms will feed on the fish and leave a wound on the fish that can get infected. 

There are also other types of diseases including bacterial infections and fungal infections diseases that can infect Killifish. But the cause of most, if not all, of these diseases, is the negligence of the aquarists that lead to disease. 

Most diseases can be prevented if the aquarists provide proper care for their fish. To prevent diseases in an aquarium, it is important to keep the water clean and free of pollutants. Regular water changes and filtration will help to keep the water quality high and reduce the chances of fish getting sick. 

You should never add new fish to your main tank without quarantining them properly. The fish sold at pet stores often carry some sort of disease or parasite that can easily spread into your tank. By quarantining the fish you are actively eliminating one of the main causes of disease in killifishes

Breeding Killifish

Breeding killifish is easy and can be a rewarding task. To breed Killifish fish in an aquarium, start by setting up a breeding tank with plenty of moss. These fish lay their eggs in moss or mud in the wild. 

Select a pair of healthy adult killifish and introduce them to the breeding tank. The female will lay her eggs in the moss, and the male will fertilize them. Once the eggs are laid you can remove the parents from the tank. 

The fry will be free-swimming right after being hatched and can be fed baby brine shrimp or other small foods.

Tank Mates

Killifish are generally peaceful towards other tank mates; although there may be some aggression between males of the same species. They are also fast swimmers and can outcompete other fish for food. 

It is important to house similar-sized species with your killifish that have a similar personality. The fish also have to be fast swimmers as killifish can be nippy at some times. Considering these here are our top picks of tank mates for these tiny guys:

• Most types of plecos
• Mollies
• Platies
• Rainbow Fishes
• Rainbow Shark
• Neon Tetra
• Vampire Shrimp
• Bamboo Shrimp

Conclusion

Killifish are unique fish that can make great additions to any aquarium. They are relatively easy to care for but are not beginner fish. So you should only try them if you have some experience with fish. Killifish are known for their vibrant colors and patterns, which can add a splash of color to any aquarium.

References:
Killifishes (Fundulidae)
What is a Killifish?
Fundulus grandis (Baird and Girard 1853) Family Fundulidae