7 Great Companion Species for Killifish

Are your killifish looking for calm, compatible tankmates to share their space without stress or conflict in the aquarium?

Killifish do best with peaceful species like neon tetras, pygmy corydoras, and ember tetras. These companions are small, non-aggressive, and thrive in similar water conditions, making them ideal choices for a balanced, low-stress tank environment.

Discover which seven species offer the best companionship while keeping your killifish comfortable and your aquarium community thriving.

Ember Tetras

Ember tetras are one of the most peaceful species you can keep with killifish. Their calm nature and small size help them blend well into the tank without bothering other fish. They enjoy swimming in schools and do best when kept in groups of at least six. Their vibrant orange color adds a gentle contrast to a planted tank, which can make your aquarium look more lively. Ember tetras prefer similar water conditions to most killifish, including soft, slightly acidic water and moderate temperatures. Since they tend to stay in the middle of the tank, they won’t compete for space.

Ember tetras are not aggressive eaters, so they won’t outcompete your killifish for food.

Their quiet presence helps reduce stress for killifish, especially in well-decorated tanks with hiding spaces. Watching a group of ember tetras move together brings a sense of calm, and their gentle swimming patterns encourage a peaceful atmosphere. When feeding, offer micro pellets or crushed flakes small enough for their tiny mouths. They’re generally healthy and easy to care for, which makes them a great choice for both beginners and experienced keepers. With proper maintenance, ember tetras can live up to two years, adding both movement and color to your tank without overwhelming its balance.

Pygmy Corydoras

Pygmy corydoras are small bottom dwellers that spend their time foraging along the tank floor, making them excellent cleanup helpers.

They are incredibly peaceful and prefer the safety of numbers, so keeping them in groups of six or more is important. Pygmy corys won’t compete for territory with killifish since they inhabit different levels of the tank. They are also small enough not to alarm your killifish, and their soft movements keep the environment calm. Their scavenging habits help reduce leftover food and waste, which can improve water quality. Pygmy corys enjoy soft, sandy substrates and hiding areas like plants or driftwood. Feeding them is easy—just provide sinking micro pellets or frozen foods like bloodworms. While they may be shy at first, they become more active and visible once settled. Their gentle personality and practical role make them a reliable addition to a well-maintained community tank.

Neon Tetras

Neon tetras are small, calm schooling fish that add bright color without creating tension in the tank. They stay mostly in the middle to upper levels and rarely bother other species, including killifish.

These fish do best in schools of at least six to eight. Their shimmering blue and red stripes add a vibrant touch, especially against a background of green plants. Neon tetras are not aggressive feeders, so they won’t outcompete killifish during mealtime. They enjoy soft, slightly acidic water and temperatures similar to killifish, which makes care routines easier. Feeding is simple—use fine flakes or micro pellets. These tetras are sensitive to sudden changes in water conditions, so gradual acclimation is important. Keeping the lighting soft and tank décor dense helps reduce their stress and encourages natural schooling behavior. They’re active but peaceful, which helps maintain a steady balance in community tanks.

When comfortable, neon tetras display smooth, synchronized swimming that gives the aquarium a steady rhythm. They coexist well with killifish because they don’t disturb other species or compete for bottom space. Their activity level brings visual interest without raising aggression or stress levels. With consistent care and clean water, neon tetras usually live up to five years. Their peaceful behavior and compatibility make them an easy and attractive choice.

Harlequin Rasboras

Harlequin rasboras are easy to care for and stay peaceful in community setups. They like to swim in groups and show vibrant copper and black colors.

They tend to stay in the mid to upper levels of the tank, rarely venturing near the bottom where killifish may rest. This separation reduces interaction stress between species. Harlequin rasboras enjoy planted tanks and benefit from soft, slightly acidic water, just like killifish. They are not fast eaters, which makes feeding time smooth and relaxed. Keeping them in a school of six or more helps them feel safe and display natural behavior. They appreciate hiding spots and swim through open areas in small bursts. These rasboras also respond well to stable tank conditions and require minimal special attention. Their calm energy and attractive colors bring life to the tank while keeping things peaceful for your killifish.

Chili Rasboras

Chili rasboras are very small, peaceful fish that rarely cause issues in a shared tank. Their calm behavior and bright red color make them visually appealing without disturbing tank dynamics. They enjoy swimming in groups and stay active in the middle of the tank.

They prefer soft water with low current and feel secure in planted tanks. Chili rasboras are shy at first but gain confidence in larger groups. They are also slow eaters, so offering powdered or micro foods works best. Their presence adds movement and color without disrupting your killifish’s routine.

Clown Killifish

Clown killifish are top-dwelling fish that often stay near the surface. They are peaceful and tend to keep to themselves, making them easy companions for other killifish species. Their striped bodies and small size help them blend into the tank. They also thrive in gentle, low-flow water with plenty of plants.

Least Killifish

Least killifish are calm, tiny livebearers that do well in peaceful community tanks. Their small size and low activity level make them unlikely to bother other fish.

FAQ

Can killifish live with other species in a community tank?
Yes, killifish can live peacefully in a community tank as long as their tankmates are calm, small, and non-aggressive. Ideal companions are species that do not compete for the same space or food. It’s important to avoid fast or aggressive fish, as killifish are easily stressed. Providing plants and hiding spots helps them feel safe and secure. Matching water parameters like temperature, pH, and hardness also helps reduce tension. Keep in mind that male killifish can be territorial, so careful planning and observation are key when adding new fish to the tank.

Do killifish get along with shrimp or snails?
Killifish can live with snails, especially nerite snails, without issues. However, they may eat small shrimp, such as baby cherry shrimp. Adult shrimp sometimes survive if the tank is heavily planted, giving them places to hide. If you want to keep shrimp and killifish together, choose larger shrimp species and provide lots of cover. Mosses, caves, and driftwood offer safe zones. Even with these precautions, expect some shrimp losses. Snails, on the other hand, help keep the tank clean and are not seen as food by most killifish, making them a safe and helpful addition.

How many killifish should be kept together?
This depends on the species. Some killifish do best in pairs, while others can be kept in small groups. Males may show territorial behavior, especially in smaller tanks. A common setup is one male with two or more females to spread out attention and reduce stress. For group species like clown killifish, small schools of six or more are best. Always research your specific type before choosing tankmates or group sizes. Having enough space and visual barriers like plants or rocks can also help reduce aggressive behavior between males.

Can different species of killifish live together?
It is possible, but not always recommended. Some species have different temperaments and water needs. Aggression may also increase when multiple males from different species share the same space. If you want to mix species, choose ones with similar care requirements and gentle behavior. Use a large, well-planted tank to give them enough space. Always monitor for signs of stress or aggression after introducing new fish. Some hobbyists separate males or keep different species in species-only tanks to avoid problems.

What tank size is best for keeping killifish and their companions?
A 10-gallon tank is suitable for a pair or small group of killifish, along with a few peaceful companions. Larger tanks, like 20 gallons or more, are better for community setups, especially if you’re keeping several species together. More space allows each fish to claim a comfortable zone. It also helps maintain stable water parameters. A planted tank with floating plants, driftwood, and soft lighting creates a safe and calm environment. Even smaller tanks can work if you stock carefully and keep up with maintenance.

What kind of food is best for killifish and their tankmates?
Killifish enjoy a mix of live, frozen, and high-quality dry food. Brine shrimp, daphnia, and bloodworms are popular options. Many killifish have small mouths, so food should be tiny or crushed. Companions like tetras, rasboras, and corydoras can also eat similar foods. Sinking pellets work well for bottom dwellers, while floating options suit surface feeders like clown killifish. Feed in small amounts once or twice daily. Overfeeding can harm water quality, so remove uneaten food promptly. Offering a variety of foods helps keep all fish active and healthy.

Do killifish need a heater or filter in their tank?
Most killifish species need a heater, as they prefer stable temperatures around 72–78°F. Sudden changes can stress them out. A gentle filter is also helpful, especially in community tanks. Sponge filters are a good choice—they provide soft flow and protect smaller fish from being sucked in. While some killifish can be kept in low-tech setups, filters improve water quality and oxygenation. A heater ensures consistent conditions, which supports the health of both killifish and their companions. Regular maintenance and monitoring are still important, even with equipment in place.

Final Thoughts

Choosing the right companions for your killifish helps keep the tank peaceful and healthy. Not all fish are a good match, so it’s important to focus on calm, non-aggressive species that enjoy similar water conditions. Small schooling fish like ember tetras, neon tetras, and harlequin rasboras usually work well because they don’t compete for territory or food. Bottom dwellers such as pygmy corydoras also make good tankmates since they stay out of the way and help clean up leftover food. Adding peaceful surface dwellers like clown killifish or least killifish can complete the tank without creating stress or conflict.

Every tank is different, and it’s helpful to watch your fish closely after adding new species. Some killifish may become territorial, especially males, so providing plenty of plants, hiding spots, and open swimming areas helps lower stress. A calm environment gives each fish a place to feel safe. Always introduce new fish slowly, and make sure to match temperature, pH, and hardness. Keeping up with water changes and feeding a balanced diet also supports a healthy tank. Even peaceful fish can become stressed if the water is poor or food is limited, so care routines play a big role in long-term success.

Killifish can thrive in a well-planned community tank when paired with the right companions. With the proper setup and a bit of care, you can build a tank that is both calm and colorful. Watching peaceful fish swim together in a balanced environment is rewarding and relaxing. Whether you’re just starting out or have more experience, selecting gentle, compatible species makes a big difference. A well-matched tank allows your killifish to stay active, healthy, and stress-free, while also creating a space you can enjoy every day.