Arnold's killifish

Care at a glance

Overview

Arnold's killifish is a robust, brightly coloured killi for a pair or a small harem of one male to two or more females. It keeps to the middle and lower levels among plants and wood, and it is a determined jumper, so a tight cover is essential. It is mostly peaceful and suits a quiet species tank or the company of small, gentle fish that will not outcompete it at feeding time. Offer a varied diet of live and frozen brine shrimp, daphnia, bloodworm, tubifex, and whiteworm, with some dry food accepted. A pair does well in a tank from about 54 liters, more if you keep several females.

In the wild

Arnold's killifish is largely restricted to the swampy fringes of the Niger Delta in Nigeria, a world of slow, soft, tannin-stained water over leaf litter. Match it with a dark, heavily planted tank, plenty of cover, gentle flow, and floating plants to soften the light. Keep the water soft and acidic to neutral, about pH 5.5–7.0, and warm at 20–25 C, adding leaves or peat to hold the colour and chemistry it likes.

Good to know

Fundulopanchax arnoldi is a member of the family Nothobranchiidae and grows to around 7.5 cm, the male far more colourful than the plainer female. It is a semi-annual soil spawner: eggs are laid into peat and given a semi-dry incubation of several weeks before hatching, which places its breeding at a moderate level of effort. Well kept adults can live two to three years, long for a fish tied to seasonal water.

Did you know

The species is named for Johann Paul Arnold, a German aquarist who helped popularise killifish keeping in the early twentieth century, a reminder that the hobby around these fish is now more than a hundred years old.

Tank mates

Arnold's killifish is a mostly peaceful, social species that keeps to the middle. These picks match on water type, temperature, pH, size and temperament.

• Filament moth catfish

  Hara filamentosa

  Freshwater

  2.4 in (6 cm)14 gal (54 L)68–79°F (20–26°C)
• Paraguay black otocinclus

  Otothyropsis piribebuy

  Freshwater

  1.4 in (3.5 cm)14 gal (54 L)68–79°F (20–26°C)
• Narayan barb

  Pethia narayani

  Freshwater

  1.8 in (4.5 cm)14 gal (54 L)68–77°F (20–25°C)
• Redspotted panchax

  Epiplatys lamottei

  Freshwater

  2.8 in (7 cm)14 gal (54 L)68–77°F (20–25°C)
• Pridi loach

  Schistura pridii

  Freshwater

  1.8 in (4.5 cm)14 gal (54 L)68–77°F (20–25°C)

• 

  Crescent gambusia

  Gambusia hurtadoi

  Freshwater

  2 in (5 cm)14 gal (54 L)68–79°F (20–26°C)

Check the full mix in the stocking calculator

Common questions

Related species

• Delta killifish

  Fundulopanchax deltaensis

  Freshwater

  3.1 in (8 cm)14 gal (54 L)68–77°F (20–25°C)

• 

  Amiet's lyretail

  Fundulopanchax amieti

  Freshwater

  2.8 in (7 cm)14 gal (54 L)68–77°F (20–25°C)
• Fallax killifish

  Fundulopanchax fallax

  Freshwater

  3.5 in (9 cm)14 gal (54 L)68–77°F (20–25°C)

• 

  Plumed lyretail

  Fundulopanchax filamentosus

  Freshwater

  2.4 in (6 cm)20 gal (75 L)68–75°F (20–24°C)
• Walker's killifish

  Fundulopanchax walkeri

  Freshwater

  2.4 in (6 cm)14 gal (54 L)68–77°F (20–25°C)

• 

  Steel Blue Killifish

  Fundulopanchax gardneri

  Freshwater

  2.2 in (5.5 cm)21 gal (80 L)70–79°F (21–26°C)