Elongate killifish
Titanolebias elongatus
The Elongate killifish exhibits a slender body, vibrant yellow-green coloration, and elongated dorsal fin, making it distinctive among killifish species.
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About the Elongate killifish
A giant annual killifish from the La Plata basin, it can top out around 22 cm and throws its weight around like a little predator. The cool part is the annual life cycle - adults spawn into peat or mud, eggs sit dry for months, then hatch with the rains.
Also known as
Quick Facts
Size
22 cm TL
Temperament
Semi-aggressive
Difficulty
Expert
Min Tank Size
30 gallons
Lifespan
6-12 months
Origin
South America
Diet
Carnivore - live and frozen invertebrates; will take small fish
Water Parameters
16-25°C
6.5-7.5
6-15 dGH
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Calculate heater sizeCare Notes
- Give a single Elongate killifish at least a 30-gallon tank; they can reach about 22 cm and throw their weight around, so extra space helps.
- Run freshwater at 16-25 C, pH 6.5-7.5, and 6-15 dGH.
- Semi-aggressive predator: avoid small tankmates (they will be eaten), and only try robust, similar-sized fish if you can separate individuals at the first sign of trouble.
- Feed a carnivorous menu of live and frozen invertebrates (bloodworms, insect larvae, shrimp); they will also take small fish.
- Expect a short 6-12 month adult lifespan; plan your keeping around that reality.
- Breeding follows the annual killifish pattern: provide a peat or mud spawning medium, dry the collected eggs for months, then wet to hatch.
- This is an expert-level fish: line up steady supplies of meaty foods and peat for spawning, and be prepared to manage aggression.
Compatibility
Good Tankmates
- Large armored bottom catfish (Raphael/doradids, hoplo catfish) that handle 20-24 C and neutral water; they ignore the killifish and are too tough and bulky to be eaten.
- Cool-tolerant plecos (bulldog/rubberlip Chaetostoma, larger Ancistrus) with plenty of wood and hides; armored, bottom-focused, and not bite-sized.
- Big whiptail/twig catfish (Rineloricaria/Sturisoma types) in the 15+ cm range; peaceful, armored, and comfortable in 20-24 C, pH 6.5-7.5.
- Robust, similarly sized but not hyper-aggressive South American cichlids from cooler water (Gymnogeophagus-type), in a spacious tank with broken sight lines.
- Conspecific females with a single male (1 male with 1-2 females) in a species-focused setup; this is the safest and most natural pairing.
Avoid
- Small community fish under about 10 cm (tetras, rasboras, danios, guppies) and any fry; they will be hunted or swallowed.
- Shrimp and other small invertebrates, and crayfish/crabs; shrimp will be eaten, and clawed inverts can injure the killifish at night.
- Multiple adult males of Titanolebias elongatus in modest tanks; strong male-male aggression leads to fighting and injuries.
- Other top-dwelling predators or very territorial fish of similar size (pike cichlids, gar-like characins, large surface killifish); direct competition and biting.
Elongate killifish (Titanolebias elongatus) is a giant annual killifish from South America. It reaches about 22 cm TL, behaves like a small predator, and is best for expert keepers. Adults live 6-12 months, so planning ahead matters. Minimum tank size is 30 US gallons.
This species follows an annual cycle: adults spawn into peat or mud, the site dries, and the eggs wait through the dry season before hatching with the rains.
Origin and natural habitat
Titanolebias elongatus comes from the La Plata basin in South America. In nature it occupies temporary wetlands and pools that form with seasonal rains and then dry out. That boom-and-bust habitat explains both its short adult lifespan and its tendency to hunt vigorously while conditions are good.
Tank setup and water
Give this fish room and structure. A 30-gallon tank is the floor for a single adult; prioritize footprint over height. Break up sightlines with sturdy decor so the fish can claim space and you can deflect aggression. Use a tight-fitting lid, as many killifish will jump.
Water parameters known to suit this species are on the cooler, slightly soft to moderately hard side: 16-25 C, pH 6.5-7.5, hardness 6-15 dGH. Provide gentle circulation and stable, clean water. If you intend to collect eggs, offer a container of peat or fine mud-like medium for bottom spawning.
Diet and feeding
A strict carnivore. Offer substantial live and frozen invertebrates such as worms, insect larvae, and shrimp. It will take small fish. Rotate foods for better condition and avoid relying on feeder fish, which carry disease risks.
Behavior and tankmates
Semi-aggressive and very predatory. Expect it to throw its weight around and to view smaller fish as food. A species-only setup is the safest approach. If you attempt a community, choose robust, similarly sized fish that are too large to be swallowed, and be ready to separate individuals if harassment escalates.
Do not house with small tetras, rasboras, shrimp, or delicate fish. Predation is likely.
Breeding
Captive breeding is based on its annual strategy. Adults deposit eggs deep in a peat- or mud-like medium. Keepers typically provide a removable container of peat, allow spawning, then lift the medium and store it damp for a dry period. After storage, wetting the medium triggers hatching. Because adults live only 6-12 months, begin spawning attempts early in their lives and maintain multiple batches of eggs to stagger hatches.
Problems to watch for
- Short lifespan: plan a breeding schedule or accept that this is a seasonal display fish.
- Heat stress: sustained high temperatures can be hard on an annual killifish; stay within 16-25 C.
- Aggression and predation: provide cover, avoid small tankmates, and be prepared to separate fish.
- Water quality: heavy, meaty feeding loads the filter. Keep up with maintenance and avoid overfeeding.
- Jumping risk: keep the tank tightly covered.
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