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Complete Killifish Care Guide for Beginners

Complete Killifish Care Guide for Beginners

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This post is written to the author's best knowledge and is not intended to be used in place of veterinary advice. In addition, this post may contain affiliate links. As an Amazon Associate I earn from qualifying purchases.

Killifish are very neat-looking fish that many people keep in their aquariums. You might be looking for some fish to add to your fish tank soon.

If you’re considering adding some of these fish to your tanks, it’s good to learn about them first. You always want to know as much as you can about fish so you can take care of them properly.

Keep reading to learn everything that you need to know about killifish care. You’ll learn about the tank requirements, how to feed the fish, and much more.

Once you’ve acquired the necessary information, you’ll feel confident about caring for these fish. It might also help you to decide whether killies are right for you, especially if you’re still on the fence about buying some.

Are Killifish Easy to Care For?

If you’re looking for fish that are simple to care for, killifish will be quite appealing to you. Overall, these fish are very hardy and they don’t have any special care needs to take note of.

You just need to meet the basic care needs of the fish to help them thrive. This means keeping them in the right water conditions, feeding them appropriate food, and keeping the fish tank clean.

The one problem that can cause these fish to die is a dirty tank. These fish won’t tolerate dirty water conditions.

When the aquarium gets dirty, it’s going to make the fish very stressed. The stress will make them much more susceptible to various diseases.

Some of these diseases might kill the fish faster than you’d think. If the fish get diseases such as columnaris, you can treat them if you act fast.

Even so, it’s better to prevent these issues from happening in the first place. Do your best to maintain the tank properly so the water will remain in good condition.

What Tank Size Is Best for Killifish?

Killies are going to be easy to keep in tanks that are fairly small. They aren’t small enough to be kept in fishbowls, but you can keep them in 5-gallon fish tanks.

However, you can’t keep many killifish in a 5-gallon aquarium. You can fit three small killifish in an aquarium of this size.

It’s more common for people to buy 20-gallon fish tanks for these fish. This is a perfect size when you want to keep somewhere between eight and twelve fish in the tank.

If you want to keep killifish in small schools, go with a 20-gallon aquarium. It’ll give you an easy experience and it should be simpler to keep the fish tank clean as well.

Killifish Temperature

Getting the temperature right in the tank is always going to be important. The temperature of the water matters when you’re caring for fish.

If the water temperature isn’t kept in the right range, your killies aren’t going to live for as long as you’d like them to. Thankfully, it’s easy enough to keep these fish healthy and happy.

Killifish do well in water temperatures that range from 68 degrees Fahrenheit to 75 degrees Fahrenheit. It should be relatively simple to keep these fish in a tank that has warm enough water.

So long as you’re using a heater, it won’t be difficult. Of course, the water temperature isn’t the only thing you need to focus on.

Killifish pH

Getting the pH balance of the water right is important as well. When caring for killifish, you want to ensure that the pH balance stays between 6.0 and 7.0.

This information can vary a little bit depending on which species you’re talking about. Most killifish do great when the pH balance is between 6.0 and 7.0, but it’s wise to look up specific information about the type of killifish that you own or plant to own.

Do Killifish Need a Heater?

A heater is going to be required when you’re caring for killifish. Without a heater, the water would get too cool for the fish.

Killifish can survive in water temperatures that are as low as 68 degrees Fahrenheit. When you aren’t using a heater, it’s easy for the water to dip below this.

Buying a heater helps to keep your killifish safe. It also makes it so the temperature of the water remains steady.

Temperature fluctuations can be problematic for fish. When fish are exposed to fluctuating temperatures, it causes them to feel stressed.

Stress leads to issues with the fish getting sick, and this is something that you want to avoid. Get a simple heater for the tank and your killies will be just fine.

Do Killifish Need a Filter?

There are differing opinions when it comes to whether a filter is required for killifish. Most experts agree that it’s recommended to have a filter, but some say that it’s not a requirement.

Buying a filter for the tank will make your life quite a bit easier. Using a good filter can help to keep the water cleaner.

This combined with regular tank maintenance should keep the water safe for the fish. Earlier, you learned that killies don’t tolerate dirty water well.

It’s especially important to use a filter if you’re keeping killifish in a small aquarium. For instance, using a 5-gallon aquarium would make it much harder to keep the tank clean without using a filter.

You might be able to get away without using a filter if you’re willing to do frequent water changes. Most fish owners agree that this will be inconvenient.

Buying a filter for a small fish tank isn’t difficult. You shouldn’t have to spend much cash to get a high-quality filter that can get the job done.

Killifish Natural Habitat

The natural habitat of killifish is quite interesting. Most types of killifish live in swampy conditions.

They can often be found in low-flow lakes or streams. It’s also common for their natural habitat to be covered in floating plants or various types of foliage.

The bodies of water that are home to these fish usually have very low light levels. Also, they’re a bit on the cool side.

When looking at the water itself, you’ll find that it’s quite soft. The water is going to be a bit acidic because of the nearby plants and foliage.

Copying the natural water conditions will take a bit of work. You can use reverse osmosis to purify the water and get rid of minerals.

You might wish to add some aquatic plants to the tank as well. There are many plants that will work well for killifish tanks such as java ferns, hornwort, and duckweed.

Killifish Water Parameters

Getting the water parameters right will allow killies to thrive in your fish tank. There are many things to focus on.

The temperature of the water should stay between 68 degrees Fahrenheit and 75 degrees Fahrenheit. You should use a heater to keep things safe for the fish and maintain a stable temperature.

The pH balance should stay between 6.0 and 7.0. Be sure to test the pH balance of the water regularly so you can make changes if necessary.

The hardness of the water should be between 4 and 15 dGH. Make sure that the water flow is low in the tank to try to copy the natural habitat of killifish.

Killifish Water Hardness

The water needs to be relatively soft for killifish. You should have the water be between 4 and 15 dGH.

What Substrate Do Killifish Need?

Choosing the right substrate can make a difference when caring for these fish. Ideally, you want to choose a sandy substrate.

A sandy substrate works nicely when keeping killifish in a community tank. Many types of fish like sandy substrate.

Some say that killifish do even better with peat moss as the substrate material. Peat moss is nice because it can absorb minerals and help to keep the water soft enough.

In some ways, peat moss is going to be more useful than sand. However, it might not matter much if you’re using reverse osmosis to soften the water.

What Should You Feed Killifish?

Feeding killifish is another important part of the process. If you don’t feed these fish well enough, they’re not going to stay alive in your fish tank.

Killifish are carnivorous, and that means that you need to feed them meaty foods. These aren’t fish that can be fed nutritional pellets and fish flakes.

You must buy either frozen foods or live foods for these fish. There are many meaty foods that killifish like to eat.

They’re known to eat brine shrimp, bloodworms, and water fleas. You can buy what you need from pet stores that sell fish food.

It’s wise to mix up the types of food that you give to these fish. So you shouldn’t feed them one type of food exclusively.

Doing so can lead to issues with malnutrition. Be sure to mix things up often enough.

It’s best to feed killifish twice per day. You want to give them as much as they can eat in two minutes.

Does Killifish Care Differ Based on Species?

One thing to keep in mind is that there are different types of killifish. Earlier, you learned that different types of killifish will have slightly different care needs.

Killifish are a rather diverse group of fish. There are more than 1,000 species that fall under the killifish category.

Since there are so many killifish types out there, it isn’t going to be possible to cover them all. It’s best to look up information about specific types of killifish when you plan to buy them.

The information above is general information that should apply to many popular types of killifish. There’s a chance that some killies might like the pH balance or water temperature to be slightly different.

What Are the Most Popular Types of Killifish?

There are many types of killifish that people like to keep in their aquariums. Some of them are more popular than others, though.

Neon-stripe lampeye killifish are rather small, and some people love them for that reason. They’re very pretty fish that can be kept in small tanks.

You’ll love how their eyes look. They have eyes that look like they’re glowing in an aquarium setting.

Clown killifish have black and yellow stripes that help them to stand out. The patterns on their tails sort of look like a rocket that’s taking off.

Red-striped killifish have blue bodies with red stripes. These are among the best options for those who are new to caring for killifish because they’re easy to take care of.

Lyretail killifish are going to look very pretty in your fish tank. They’re bright orange and feature both black spots and lines on their fins.

Finally, golden wonder killifish are beautiful due to their golden color. It’s also nice that these are among the most affordable killies that you’ll find in pet stores.

Killifish Aren’t Common

Note that killifish aren’t the most common type of fish. Many types of killifish are considered to be rare.

The rarity of the fish makes it hard to find them. You often won’t be able to find killies in local pet stores.

Sometimes you might see some killifish being sold locally. However, the fish aren’t likely to stick around for long.

The only reliable way to buy killifish is to turn to online fish retailers. You should be able to find some being sold at reasonable prices online.

As you’d expect, some killies are going to be rather pricey. The rarer varieties are going to cost you more money.

How Big Do Killifish Get?

Most types of killifish are going to stay small. You’ll find that common killifish will grow to be between one and two inches long on average.

Since they’re not all that big, they can be kept in fairly small tanks. It should be noted that the size of killifish will differ somewhat depending on the species that you’re discussing.

For example, golden wonder killifish can grow to be two and a half inches long. Clown killifish will only grow to be just under one and a half inches long.

There are killifish out there that grow to be a fair bit longer than two inches. Most of the common types of killies aren’t going to be very large, though.

Killifish Tanks Need to Be Covered

Caring for killifish can be a lot of fun. These fish can be enjoyable to watch.

They’re rather active fish and it’s interesting to watch them swim together. Killies are also well-known for their jumping.

Since these fish like to jump, it’s imperative to buy a cover for the fish tank. If you don’t cover the fish tank, some of the killies might wind up leaping right out of the water.

You don’t want your fish to die. Ensure that you have a secure lid on the fish tank at all times to protect the fish.

Are Killifish Aggressive?

Sometimes killifish can be aggressive. Males are known to be aggressive toward each other.

They do this because they compete to see who is the dominant fish in the tank. It’s also common for fish to compete for mates.

You’ll find that killifish can act aggressively toward other types of fish as well. It’s normal for killifish to fight with fish that look too similar to themselves.

So you need to pick tank mates for killifish carefully. You don’t want to make the wrong moves and wind up with dead fish.

Another thing to keep in mind is the size of the tank. When you keep killifish in tanks that are too small, it’ll make it more likely that they will become aggressive.

Do your best to buy a fish tank that is appropriate for the number of killifish that you want to own. This should make things far more manageable.

Can Killifish Be Kept Alone?

It’s not advisable to keep killifish by themselves. Keeping only one killifish in the tank would be cruel.

These fish are used to living in small schools. Many people say that it’s best to keep between eight and twelve of these fish in the tank.

When buying killifish, you want to make sure that you have the right mixture of male and female fish. Earlier, you heard that male killifish can be aggressive toward each other.

Often, this aggression will be related to competing for the attention of females. If the female killifish outnumber the males three to one, it’ll be easier to avoid fighting.

Are Killifish Good Community Fish?

Killifish can be good community fish. You simply need to ensure that you pick out good tank mates for them.

When the environment is well taken care of, it’s easy for these fish to stay fairly peaceful. Below, you’ll learn about some of the best tank mates that you can choose for killifish.

It’ll be fun to keep killies as part of a community tank. So long as you do the necessary research, you should have a good experience with this.

Kuhli Loaches

Kuhli loaches are excellent tank mates for killifish. They work out so well because they’re peaceful fish that spend most of their time at the bottom of the tank.

Killifish like to stay near the top of the tank. You’ll never see killies and kuhli loaches come into conflict.

Cory Catfish

Cory catfish are another great bottom-dwelling fish to consider. These fish are also peaceful, and they can be great fish to own.

They’re good tank mates that can be put in many types of community tank settings. You won’t be disappointed if you choose to buy some cory cats for your fish tank.


Rasboras work out well as tank mates for killifish. This is because they’re fish that are very close to the same size.

It’s also nice that rasboras are pretty fish. They should look very nice in the aquarium with your killifish.


Tetras get along pretty well with killifish. Since they’re around the same size, they shouldn’t wind up fighting with each other.

There are many colorful types of tetras that you can choose from. These fish are a fantastic way to add some aesthetic appeal to your aquarium.

Never Put Angelfish in the Same Tank as Killifish

Angelfish are gorgeous and popular aquarium fish. If you’d like to keep them with your killies, it’s best to take a step back and think.

Sadly, angelfish are rather aggressive. They’re types of cichlids that are known to be bullies.

Angelfish don’t bully every type of fish that they see, but it’s very likely that they would harm killifish in a community tank setting. This is a pairing that simply won’t work out well.

Barbs Won’t Work Either

Barbs are another popular type of fish that will simply be too aggressive and large for killies to handle. The barbs might wind up killing the killifish if you aren’t careful.

Since barbs are aggressive and somewhat big, they’ll stress the killifish. This can lead to the killies experiencing various health issues.

Final Thoughts

After learning more about killifish, it should be easier to take care of them. Killifish are interesting fish that you can enjoy keeping in your home aquarium.

If you manage to find some of these fish, it’s a good idea to buy them. They aren’t that hard to take care of even for beginners.

So long as you get the water parameters right, it’s easy to keep them in good health. Focus on getting the temperature, pH balance, and water softness where it needs to be.

Feeding the fish is easy enough, but you’ll have to spend cash on live food or frozen food. This is likely going to be more expensive than just buying fish flakes.

Since killifish are carnivorous, they’ll only eat meaty foods. Be sure to mix things up so that the killies don’t experience malnutrition.

If you wish to keep killies in community tanks, pick compatible tank mates. They can get along with peaceful bottom-dwelling fish such as cory cats and kuhli loaches.

It’s also fine to put them in fish tanks with tetras and rasboras. You must avoid putting them in community tanks with aggressive fish such as angelfish and barbs.

Killies aren’t meant to live alone. You always want to keep them in small groups.

You should keep more female fish in the tank than males. This helps to keep the males from feeling the need to fight.

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