Killifish are some of the most beautiful, amazingly, brilliantly colored fish you can keep in an aquarium. They come in a wide range of types of killifish with a wide range of physical characteristics, too, so you can choose from a huge number of fish with a lot of different colors and body types.

And if you’re wondering if are killifish hard to keep, you’ve come to the right place. We’ll answer this along with what do you feed killifish, and how long do killifish live for, clown killifish lifespan, are killifish aggressive, and more.

Let’s take a look at these beautiful little fish and help you decide if these are a great choice for your home aquarium or not.

Quick Intro to Killifish

FamilyAplocheilidae, Cyprinodontidae, Fundulidae, Profundulidae, and Valenciidae
Scientific NameAphyosemion striatum
Other NamesRed striped killifish, Striatum killifish
Care LevelEasy to Difficult, depending on specific species chosen
Fundulus_cingulatus
By Howard Jelks – http://cars.er.usgs.gov/pics/nativefish/nativefish/nativefish_0.html, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=649490

Natural Habitat, Identification, and Where to Buy

When you look at brightly colored fish, the automatic thought is that they’re tropical – and in this case, that is true, but not marine tropical. Killifish freshwater fish have different needs than marine tropical fish.

You’ll naturally find these little fish on every continent – save Australia and Antarctica – in the warmest water regions in tropical and semi-tropical environments.

Killifish typically are found in temporary pools, swamps, creeks, brackish estuaries, and shallow streams. Generally, where you find lots of overhanging trees and shrubs, with subdued lighting and cooler temperatures, there’s a chance you’ll find some killifish.

Interestingly enough, though, some species even inhabit the Southwestern United States in desert pools with water temperatures of 90 degrees and higher even. So, seriously, you could find these little guys just about anywhere in the wild.

Killifish are egg-laying fish that include a number of species of livebearers that you’re already familiar with, including guppies and platies. You’ll find similarities in these fish like dorsal fins that are closer to the tail, flattened heads and backs, and an upturned mouth. These are all developed for acquiring insects for dinner that fall from lower hanging branches or those yummy mosquito larvae they love noshing on.

Good news on care for these guys is that generally clown killifish care looks the same as blue gularis killifish care or the same for gardneri killifish care or golden wonder killifish care.

Fundulopanchax_gardneri
By Violaine2, France – Self-photographed, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1891516

When you’re ready to buy your killifish, you can find them on a ton of different sites including:

Optimal Water Conditions for Killifish

Water Temperature72-75 degrees F
Water Flow RateExtremely low
pHBetween 6.6 and 7.2
Water Hardness122-162 ppm

Tank Setup

Minimum Tank Size20+ gallon per pair
Optimal Tank Size25+ gallon for more than one pair
Optimal Tank ShapeShallow, long rectangular fish tank
Recommended Filter TypeLow-powered filtration that keeps the water and air flow low, such as HOB or sponge filters.

Killifish live naturally in a wide range of places, so they have a fairly wide range for temperature, fish tank size, etc., but there are optimal parameters you should aim for. Generally speaking, temperatures between 72 and 75 degrees will suit most Killifish species. The pH, however, is where you’ll find the wider variance. Depending on where the fish was obtained, it could be anything from 6.6 to 7.2 as the ideal. Generally speaking, however, 7.0 is your target for killifish. 

Creating the Landscape

As you build the habitat for your killifish care, you’ll want to keep several things in mind. 

First off, you can technically keep some species of killifish in very small tanks (5-10 gallons), but this should only be done by folks who are already knowledgeable on keeping killifish, and specifically familiar with keeping nano tanks. If you want to keep more than one male, I’ll add, you must have a larger setup. They are generally peaceful fish, but anything smaller than 20 gallons won’t permit the males to have enough territory to keep from fighting each other.

Killifish naturally live in low light settings, as well, so you need to keep their homes in low light areas, with minimal setups. Be sure to provide them with floating plants and use dark substrate to emulate their natural habitat. These things will help to give them a stronger allusion to their natural home, which will help reduce stress, improve health, and lengthen lifespans.

And a huge thing to remember with these guys is that they must have lids on their fish tanks at all times. They are jumpers and will escape and bring harm to themselves otherwise!

For decorations, you’ll want to consider things like treated driftwood and peat moss that can help soften the water and keep the pH lower while providing them natural landscaping items that will feel comfortable to them. Rocks are also a great option, especially if you can mimic some cave-like structures for them to use in times of stress.

Best PlantsJava ferns, Java moss, African water ferns, Anubias, Indian ferns, Hornwort, Najas
Best LightingLow lighting
Best DecorationsGo with dark substrate, specifically gravel with sand, is ideal. Other decorations to include are anything that will provide “overhang” similar to overhanging branches from their natural, wild habitats.
Decorations to AvoidAnything with sharp corners and edges that might harm their fins and tails.

Physiological Considerations for Killifish

Size2 to 2.2 inches
Lifespan3 months to 5 years, depending on species
TemperamentMost species are peaceful
Preferred Tank RegionBottom of tank
Scale Thickness The majority of species have round scales and no barbels. No special considerations need to be taken, apart from avoiding sharp décor items.
Gill ConsiderationsNo special care is needed, apart from keeping their water clean and other general precautions employed for all fish species.
Swimbladder ConsiderationsNo special considerations need be taken, apart from making sure that they are not overfed, and their tanks and cleaned regularly, as should be done for all fish with swim bladders.
Fin Shape ConsiderationsGeneral considerations for killifish fins are required, though some species have longer tails and fins. For those with longer fins and tails, extra care should be taken to avoid rocks with sharp edges and any décor items that may snag on these flowing fins. Fin nipping species should also specifically be avoided as tank mates for these fish.

Since Killifish is a huge group of fish species, you’ll find their appearance and types vary greatly. They are particularly known for their striking, vibrant colors, however, along with their intriguing body patterns. The heads of sexes are flat on the top, and they have a mouth that’s on the very tip of their faces. Their scales are round and do not have barbels unlike many fish species.

They have long, cylindrically shaped slender bodies, with some having rounded, slightly shorten than expected fins, while others have long, broader fins. Most killifish are about 4-inches in length when mature, though, of course, there are exceptions, with some reaching ten inches in length.

These agile swimmers prefer the bottoms of their tank, as their natural habitat is usually very shallow and slow moving. 

Types of Killifish

Killifish truly are a unique species of fish with so many varieties, colors, styles, and appearance that they truly add variety, even within species, to any aquarium.

And while there are hundreds of species in the Killifish world, this several are the most commonly preferred by hobbyists.

  • Bluefin Notho
  • Neon Striped Lampeye Killifish
  • Striped Panchax
  • Blackfin Pearlfish
  • Lyretail Panchax
  • Blue Gularis
  • American Flagfish
  • Clown Killifish
  • Lyretail killifish
  • Red Killifish
  • Rainbow Killifish
  • Pearl Killifish
  • Gardneri Killifish
  • Golden Wonder Killifish

Society

Most Killifish species are fairly peaceful fish. The males will fight for superiority in their own territory or over females if they are in too small an aquarium. They generally do well in killifish community tank  with other species, but only if there are enough females to males (several each) and that their tanks are 25+ gallons for more than one pair.

If you are a newbie fishkeeper, we recommend that you keep Killifish in pairs in a species only tank (meaning only one pair of Killifish) until you’ve gotten some more experience under your belt. Or keep only one male Killifish in a community tank and avoid males of similar looking species out.

There are a number of great Killifish tank mates that they will get along with. Some of those include:

Gender, Breeding, and Reproductive Considerations

There are two types of breeding killifish. Some are annual breeders, while others are non-annual Killifish. The females are docile and can be kept in large numbers together, but the males must have enough space to prevent aggression towards one another.

Like most fish species, the males are more brightly colored than females, especially during breeding season.

Killifish are usually fairly easy to breed, when given the right setup.

You’ll need to provide them with a smaller tank for breeding, with substrate of peat moss and sand. Pair a male and a female together in the smaller tank. The female will lay eggs and bury them under the sand completely. Once this has happened, both parents should be returned to the larger tank and the eggs should be kept in this smaller, warmer aquarium for three months. Once the fry hatch, they will eat the egg sack and once this is gone, they should be fed brine shrimp.

Nutritional Needs

Killifish are carnivores. They prefer things like crustaceans, worms, crickets, and insect larvae. They specifically need live foods rather than frozen or freeze-dried foods as their foundation, which is another reason why they’re not usually a great choice for beginner hobbyists.

Balancing out their diet is also important, which means providing them with live food is necessary as their base but adding in other things to supplement will keep them healthier and happier.

Suggestions for their best food include:

  • Daphnia
  • Bloodworms
  • Brine shrimp
  • Mosquito larvae
  • Fairy shrimp
  • Black worms
  • White worms
  • Tubifex worms
Best Sustenance Food TypeLive foods such as insect larvae, crickets, and crustaceans
Additional Food For Optimal HealthAdditional frozen and freeze-dried animal protein foods like bloodworms, tubifex and brine shrimp
Special Foods and Considerations for Best Color and GrowthA solid base of live food with supplemental foods of additional protein sources like daphnia
When and How Often to Feed Fish Based on Life CycleThey should be fed once or twice daily (watch behavior to determine which), with a blend of animal protein foods. They should be fed what they can eat within a 2-minute period or less.

Common Diseases and How to Avoid and Treat Them

Before looking at more specific ailments and treatments, a note that should be kept in mind for your killifish. Despite being predominantly freshwater fish, Killifish do well with a little bit of marine salt to help keep them healthy and active. Salt doesn’t evaporate in the water, so very limited amounts are needed.

That being said, some of the common health issues that Killifish experience are due to lack of sodium. Sometimes, adding just a tiny bit of salt (1/2 teaspoon per gallon) to their fish tanks can help cure simple diseases and ailments.

Killifish are generally a fairly hardy fish, when cared for properly, but that doesn’t mean that they can’t become ill. The most common ailments that Killifish face include the following.

Ich

This common ailment for freshwater fish is the most common aquarium parasite found. Small, raised white spots pop up on the body and fins, followed by the fish rubbing against things to scratch an insatiable itch. They may also display rapid breathing, twitching, or darting around in unusual manners.

Usually, what causes ich is a sudden drop in the water temperature caused by heater malfunctions or major water changes, adding cold water during water changes, or addition of new fish into the killifish tank environment. New fish can be carriers without showing symptoms, so pay special attention to your established fish any time new ones are added for this reason.

If ich develops in the aquarium, you’ll need to treat the fish and the entire fish tank. It’s a highly contagious infection and can harm your fish badly.

The most effective way to treat ich in Killifish – and most freshwater fish – is using aquarium safe ich medication. Adjust the temperature of the water to 76 to 80 degrees, remove the carbon or other chemical filter media, and follow the recommended dosing instructions on the bottle. Keep in mind that after adding gravel and decorations, your aquarium contains about 10-15% less actual water than the gallon-size stated.

Fish Lice

Another common freshwater fish disease is fish lice. They’re technically crustaceans that have a broad, flat shell and four sets of swimming legs. They’re easy to spot, thankfully.

Infected fish will swim erratically or rub against décor items to try to get rid of them. If you notice this behavior, look closely and you’ll see the lice moving around on the scales of your fish. 

Fish lice is usually introduced into an aquarium via wild-caught or pond-raised fish. They’re common goldfish and koi, but easily infect other fish as well, including killies.

You can remove the lice using tweezers, but the whole aquarium will need to be treated to remove eggs that have been laid as well. Dimilin is a great treatment for this.

Fish Flukes

Another common ailment in Killifish and other freshwater fish is fish flukes. These parasites invade the skin and gills of aquarium fish, attaching themselves with “hooks.” They weaken and harm your fish as most parasites do, feeding off the fish.

Symptoms of fish flukes include difficulty breathing, loss of color, listlessness, excess secretions, tattered or clamped tight fins, small blood spots appearing on your fish, or flared gills.

Usually, flukes result from stress caused by poor water quality, improper diet, aggression from other fish, or overcrowding. They can also be introduced via new fish into the aquarium who weren’t quarantined properly before introduction. 

The best way to treat for fish flukes is use of Praziquantel and formalin for the aquarium.

  • Best Antibiotics: Praziquantel, Dimilin, Formalin, aquarium-safe ich medication
  • Treatments to Avoid: None specifically
  • Food Recommendations When Sick: Maintain the high protein food, focusing more on the live food options.
  • Hospital Tank or Isolation Withing the Community Tank: Quarantine any fish before introducing them into your main aquarium to help reduce the number of infections in the environment.

One More Thing to Know About Killifish

We’ve mentioned it before, but this is vital: Killifish are excellent jumpers – so they’re fun to watch! But they’re also easy to lose. Keep the lid tight on your aquarium to keep these little fish safe and healthy.

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