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Can Killifish Live With Guppies?

Try and Blame it on our love for fish, but you can’t deny that as aquarists and hobbyists, we tend to imagine the different types of aquarium fishes paired together and have them co-exist in perfect harmony.

As such, we will not judge when you stop and wonder, “Can Killifish live with Guppies?” but rather just assume that you’re deeply fascinated and in love with both.

When we talk about Guppies, they generally go well with most types of fish species, while, on the other hand, Killifish tend to be more specific regarding tank mates.

Both these fish species are generally smaller than most aquarium fishes and incredibly popular.

However, the size might be the only similarity between the two, so if you’re here seeking answers on whether these two species can be paired in the same tank, then you’re at the right place.

Read on as we delve deeper into whether Guppies and Killifish make good or bad tank mates.

Understanding Killifish

Killifish are incredibly beautiful freshwater fishes known for their vibrant mixed colors and rich evolutionary history.

This particular species, to survive in hard conditions, has developed a superpower- The eggs have the ability to survive being dried out for long periods of time.

Due to their ability to transform and adapt to numerous harsh environments and conditions, scientists use Killifish to study and research various topics such as environmental adaptations, genetics, and developmental biology.

Belonging to the family Cyprinodontidae, they are found in various parts of Asia, Africa, and North and South America in water bodies such as swamps, puddles, and seasonal ponds and are carnivores.

Today, according to Modestfish, there are approximately 1270 different species of Killifish, and they grow on an average of 1-2 inches in length, with the biggest species of Killifish being six inches.

Most of these killifish species vary and differ in fins and coloration.

Although known for adaptability, the killifish species thrive in 20-gallon tanks, ideal for only a pair of two for larger species, with 10-20-gallon tanks ideally for housing three smaller killifish.

Most killifish species thrive in 6.

0 to 7.

0 pH levels with a water temperature of 68°F to 75°F, and ideally, you need to add plenty of plants and decor to mimic their natural habitat and give them great hiding spots.

Understanding Guppies

We know and understand that Guppies are one of the most loved aquarium fishes, known to many for their vibrant colors, ease of maintenance, and being extremely social with tank mates under ideal conditions.

The average growth size of guppies is 2 inches.

They were introduced to the aquarium pet trade in the mid-1800s and used to control mosquitos for many years.

Naturally, Guppies are extremely friendly and a great pet to start with if you’re an aquarist who recently fell in love with the aquarium pet trade.

However, most people believe that since Guppies are generally docile, they do not have aggression.

This is completely false, considering you can’t have two males in the same tank without proper space and 4-6 females for each male to reduce aggression and territorial behavior.

Guppies generally survive in 20-gallon tanks that can house a maximum of 10 Guppies with proper decor and plantation for their various needs, such as hiding spots, exploration, and mating.

In addition, the ideal water temperature for Guppies to thrive in is between 74°F to 82°F and a pH level of 7.

0 to 8.

0, and they are not recommended to be tank mates with aggressive species.

Can Killifish Live With Guppies?

It is advisable not to keep Killifish with Guppies since they differ in many ways, such as their sizes, diets, characteristic traits and behavior, and tank requirements, but are similar in many ways as well.

For instance, Guppies tend to thrive in 72°F to 82°F water temperatures with a pH level between 7.

0 to 8.

0, while Killifish thrive in 68°F to 75°F with the same pH level, making them ideal.

However, male Killifish are known to be extremely aggressive and territorial, even towards their own fish species.

At the same time, Guppies are rather friendly if their conditions for ideal living are met, making them prone to get bullied or eaten if paired with aggressive species.

Experts recommend that while a 20-gallon tank is ideal for a community of 10 Guppies, the same 20-gallon tank is ideal for only 2 killifish.

Due to their size difference, most seasoned aquarists advise people to get at least a minimum of a 50-gallon tank with enough plantation and decor for hiding spots to avoid overcrowding and negate the chances of aggression or an attack.

Furthermore, people who have kept them together say that the best way for Guppies to survive with Killifish species is to own more females than males since they tend to be less aggressive.

Also, ensure that the Killifish are properly and separately fed for them to show fewer signs of aggression.

Another reason to feed them separately would be that Guppies are surface swimmers and omnivores; they might eat everything if fed together since Killifish avoid the surface, leading to aggressive behaviors from the Killifish.

However, even after careful observation of their behavior, and you see the Killifish nipping or bullying the Guppies, make sure to use your last resort of keeping them separate.

Compatibility Considerations

There are different types of Killifish species, like the golden wonder Killi, which will eat full-grown Guppies in an instant.

We might like to say that it depends on the size of both these fish species, yet some Killifish, smaller than Guppies, are prone to showing aggression towards them and get extremely territorial.

However, you have a better chance of having them co-exist in harmony if they are the same size or the Killifish smaller than the Guppies, along with certain conditions.

Conditions include being equipped with a large tank, ideally, a 50-gallon tank (for larger Killifish) to avoid overcrowding, with proper water conditions and temperatures.

If you’re dealing with nano Killifish, the ideal tank would be 10 gallons for a trio.

That said, the tank needs to be equipped with proper natural plantations and other decorative ornaments offering plenty of hiding spots.

Also, as we’ve mentioned, ensure that your Killifish do not get hungry by feeding them at appropriate times and separately.

You can also increase your chances of having them co-exist in harmony by adding more females to fewer or zero male ratios since they tend to be less aggressive.


While Killifish and Guppies may not be as similar regarding temperaments, needs, and other traits, it’s not entirely impossible for them to co-exist peacefully in your beautiful aquarium.

It may not be recommended by experts since it’s a lot of work.

Still, if you’re hell-bent on mixing these two incredibly beautiful species, then you might need to consider following the conditions mentioned in this article.

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