Dartfish

Dartfish mainly include species from the genera Nemateleotris and Ptereleotris, now classified within the subfamily Ptereleotrinae of the Gobiidae family, and formerly placed in the Microdesmidae family.

Native to the tropical Indo-Pacific, particularly New Caledonia, the Red Sea and the Pacific Islands, they inhabit areas around coral reefs over sandy substrates, where water flow is low to moderate and zooplankton is abundant.

Their elongated bodies, vibrant colours and lively swimming behaviour bring movement and vitality to the reef aquarium, while their fascinating natural behaviour makes them particularly interesting fish to observe.

Dartfish appearance, species and behaviour

Dartfish have slender, elongated bodies, with a long first dorsal fin and a well-developed anal fin. These fins are used to communicate with other members of their species, signal their presence and propel themselves through the water.

Depending on the species, adult dartfish generally reach between 6 and 14 cm in length.

They usually swim in the middle levels of the aquarium and quickly dart into a burrow or crevice when they feel threatened. This sudden movement is what gives them their common name, dartfish.

Nemateleotris

Each Nemateleotris species displays vibrant colours, ranging from pearly white to purple and deep red.

• N. magnifica: Creamy white at the front of the body, gradually transitioning through orange to deep red towards the caudal fin. Commonly known as the Firefish Goby.
• N. decora: Cool shades combining purple, pearly white and greenish highlights.
• N. lavandula: Creamy white at the front of the body, gradually transitioning to lavender and then purple towards the caudal fin.

Behaviour and care: Although Nemateleotris naturally become territorial towards members of their own species as they mature, keeping them in groups is possible under certain conditions.

• In smaller aquariums: It is preferable to keep a single individual or an already established pair to ensure peaceful cohabitation.
• In groups of three or more: This setup is suitable for large, well-structured reef aquariums of at least 300–400 litres, with plenty of shelters. A varied aquarium setup allows each fish to find its own retreat and helps reduce tension within the group.

Ptereleotris

Ptereleotris species include P. zebra, P. evides, P. microlepis and P. heteropterus, among others.

• They have elongated bodies, swim quickly and display colouration that varies between species, from zebra-like patterns to silver and deep blue shades.
• More social than Nemateleotris, they can be kept in small groups of 3–5 individuals in a spacious aquarium of at least 200 litres. Territorial interactions may develop over time, and these fish also appreciate having access to plenty of shelters.

Dartfish aquarium setup and water parameters

For optimal care, the following aquarium conditions are recommended:

• Water temperature: 24–28°C
• pH: 8.0–8.3
• Water flow: moderate
• Lighting: sufficient to bring out their colours without causing stress

Dartfish are known for their tendency to jump out of the aquarium when stressed, so a secure lid or mesh cover is essential.

The aquarium should provide several shelters and hiding places. Without sufficient shelter, dartfish may remain hidden, which can affect their colouration and alter their behaviour. Suitable reef aquarium water parameters and an appropriate minimum tank size based on the size and territorial behaviour of each species are essential.

Dartfish diet and feeding

Dartfish are planktivores that feed mainly in the water column, capturing suspended food particles before they reach the bottom.

To provide a suitable dartfish diet:

• Feed Mysis shrimp or enriched Artemia (brine shrimp) several times a day
• Temporarily reduce pump flow to keep food available in the water column for longer
• Avoid keeping them with tank mates that are too fast or competitive at feeding time

Dartfish health and compatibility

To thrive, each dartfish species should be kept with peaceful, non-territorial fish. It is advisable to limit their cohabitation with highly active or dominant bottom-dwelling fish.

In a calm environment with accessible hiding places and regular, appropriate feeding, dartfish can fully display their vibrant colours and natural behaviour in the reef aquarium.