Celebes Rainbowfish

The Celebes rainbowfish comes from Telmatherinidae, a small family endemic to the Indonesian island of Sulawesi (Celebes), and is the best-known species of this family in the hobby. Its most distinctive features are the iridescent blue stripe running along the rear half of its semi-transparent, yellowish body and, in males, lemon-yellow fins edged in black with elongated front rays.

In older sources it appears under the name Telmatherina ladigesi. It reaches 7 cm, is an active swimmer and needs clean, oxygen-rich water. It is sensitive to poor water; it needs a mature, regularly maintained aquarium.

It lives in clear streams flowing out of the limestone hills of the Maros region in southwestern Sulawesi. The water is rich in calcium, moderately hard and slightly alkaline; the flow is gentle to moderate. Its natural habitat is under pressure from agriculture and settlement.

• Volume: at least 100 liters and 80 cm in length for a school of 6–10.
• Water: 24–26°C, pH 7–8, moderately hard water. 25–30% water changes every week; avoid acidic, soft water.
• Decor: Plants along the edges, plenty of open space in the middle; rocks and roots give a natural look.
• Flow: It likes gentle to moderate flow and good oxygenation.
• Lid: It can jump; use a lid.

Omnivorous. It is fed quality flakes and small granules, frozen brine shrimp, cyclops, daphnia and small bloodworms. Live foods enhance color and the urge to breed. It takes food mostly from the surface and in midwater; feed small amounts 2–3 times a day.

Peaceful and active; it swims in groups in the upper and middle layers. Males display to each other by spreading their long fin rays and chase the females; the squabbles are harmless. It may eat shrimplets.

Good companions: Corydoras, otocinclus, bristlenose plecos, medium-sized rasboras and tetras, neon dwarf rainbowfish, blue-eye species, nerite snails.

Avoid: fin-nipping barbs, aggressive cichlids, very large and fast fish.

At least 6, ideally 10 or more individuals. A female-heavy group (2 females per male) is balanced. Having several males noticeably increases display behavior and fin color; when kept in small numbers it stays shy and pale.

A continuous-spawning egg scatterer. Females lay a small number of eggs every day on fine-leaved plants, moss or a wool spawning mop. The parents eat the eggs; move the mop to a separate container regularly. The fry hatch in about 8–12 days; start with infusoria and liquid fry food, then move on to newly hatched brine shrimp. The fry grow better in hard, clean water.

Hybridization: Because hardly any other species of its family is available in the hobby, the risk of hybridization is low; even so, keeping lines from different sources separate and passing on fry with information on their origin is good practice.

• Water quality: sensitive to the buildup of nitrate and organic pollution; the first signs are paleness and clamped fins.
• White spot: can appear after a sudden temperature drop.
• Acidic water: in soft, acidic water immunity weakens and susceptibility to disease increases.

Males are larger and more colorful; the front rays of their second dorsal and anal fins are elongated and edged in black, and the fins are bright yellow. Females are smaller and paler; their fins are short, rounded and slightly yellowish.