Forktail Rainbowfish Care Guide - Aquarium Setup, Diet & Breeding

Forktail Rainbowfish are small, lively members of the Pseudomugil family, recognised by their bright yellow fins, slender blue-green body and strongly forked tail. Mature males develop especially vivid colouration, with elongated fin rays and animated displays that make them a striking feature of a planted aquarium.

These fish are active midwater swimmers and are most impressive when kept in a group. Males regularly flare their fins and face one another in harmless displays, while females tend to show subtler colours and a more streamlined appearance. Their constant movement gives a small aquarium a lively, energetic character.

In the wild, Forktail Rainbowfish inhabit clear, shallow streams and slow-moving tributaries surrounded by dense tropical vegetation. Their natural waters may flow over sandy or muddy bottoms and often contain submerged roots, leaf litter and overhanging plants.

Pseudomugil furcatus was first described from New Guinea and has become a popular aquarium fish because of its attractive markings, manageable size and peaceful temperament. It is sometimes sold as the Forktail Blue-eye, a name that reflects its brilliant eyes and close relationship to other blue-eye species.

Forktail Rainbowfish come from freshwater streams, tributaries and swampy habitats in eastern New Guinea, particularly the Milne Bay Province of Papua New Guinea. They are native to the tropical Oceania region.

A group should be provided with an aquarium of at least 60 litres, ideally measuring around 60 cm long by 30 cm wide or more so they have uninterrupted swimming space. Use a fine gravel or sand substrate, dense planting around the sides and back, and open water through the centre. Floating plants, fine-leaved vegetation, roots and gentle filtration help recreate their sheltered stream habitat, while a secure cover is important because these active fish can jump.

Males reach up to about 6 cm (2.4 inches) in total length, while females are usually smaller at around 4.5–5 cm (1.8–2 inches).

Forktail Rainbowfish are small omnivores and should receive a varied diet of quality crushed flakes, fine micro-pellets and small frozen foods such as daphnia, cyclops and baby brine shrimp. Live foods are particularly useful for encouraging strong colour and spawning. Their small mouths mean that food should be appropriately sized, and several modest feeds are often better than one large meal.

Forktail Rainbowfish are peaceful community fish that can be housed with similarly sized, gentle species such as small tetras, rasboras, danios, smaller Corydoras, Otocinclus and other peaceful rainbowfish or blue-eyes. They do best with calm tankmates that will not outcompete them for food. Avoid large, aggressive or boisterous fish, fin-nippers and slow fish that may be stressed by their constant activity. Males can be kept together, provided the group includes several females and the aquarium offers plenty of visual cover.

Forktail Rainbowfish are egg scatterers that readily spawn among fine-leaved plants or spawning mops. Condition a group with plenty of small live or frozen foods, then provide a mop or dense vegetation for the eggs. Remove the spawning material to a separate container to protect the eggs from being eaten. Hatching usually takes around 10 to 14 days, and the tiny fry need very small foods such as infusoria or commercially prepared fry food before they are large enough for baby brine shrimp.

Males are larger and more colourful than females, with elongated dorsal, anal and pelvic fin rays, brighter yellow fin markings and a more strongly forked tail. Females are generally smaller, plainer and more rounded through the abdomen.