Celebes rainbowfish
Marosatherina ladigesi
intermediate careOverview
The Celebes rainbowfish (Marosatherina ladigesi) comes from the streams of Sulawesi (formerly Celebes) in Indonesia. It’s a slender, shimmering fish with a blue-green sheen and delicate yellow-tipped, spiky dorsal and anal fins that males extend in display. Peaceful and constantly on the move, it’s a lovely mid-water shoaler for a mature community — provided you can give it the harder, alkaline water it prefers. Like all rainbowfishes, its full colour arrives only with age.
Tank & water
A shoal needs at least 80 litres (20 gallons) of length and open swimming room.
- Hard, alkaline water: aim for pH 7.0–8.5 and moderately hard water. This is not a soft-water blackwater fish.
- Mature tank: add them only to a fully cycled, settled aquarium — they dislike the swings of a new setup.
- Warmth and flow: hold 24–28 °C with a heater and provide some gentle current from the filter; they enjoy moving water.
- Planting and light: plants around the edges with open water in the middle, and good lighting to catch their iridescence.
Feeding
An easy omnivore, the Celebes takes quality flakes and micro-pellets from the fish food range readily, and colours up best with regular live and frozen treats — daphnia, brine shrimp, mosquito larvae and cyclops. A varied diet keeps the males displaying.
Tankmates
Peaceful and non-nippy, they mix well with other hard-water, active community fish of similar size: other rainbowfishes, larger rasboras, danios, otocinclus and peaceful barbs. Avoid slow, long-finned fish that share their water needs poorly, and anything large enough to intimidate them. Always keep a group of six or more with a couple of males so they display rather than hide.
For a mixed rainbowfish tank, see our best large aquarium picks for the swimming room they need.
Common mistakes to avoid
- Keeping them in soft, acidic water
- Too small a group — colour and confidence collapse
- Adding them to an immature tank
- A cramped tank with no open swimming lane
Celebes rainbowfish — frequently asked questions
Do Celebes rainbowfish need hard water?
They do best in hard, alkaline water (pH 7.0–8.5), and some keepers add a little marine salt or extra minerals. Soft, acidic blackwater conditions are not suitable and will shorten their lives.
Why aren't my Celebes rainbowfish colouring up?
Colour develops with age, a mature tank and a group. Young fish are drab. Give them a settled tank, a shoal of six or more with rival males, good food and hard water, and the blue-green shimmer and yellow fins will strengthen over months.
How big do Celebes rainbowfish get?
Around 6–7 cm. They are slim, active swimmers, so give them length and open water rather than a small, cluttered tank.
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