Nanochromis transvestitus

Nanochromis transvestitus comes from the blackwater of Lake Mai-Ndombe in the western Democratic Republic of Congo — one of the most acidic, tannin-rich bodies of water on Earth. It earned its provocative scientific name from the striking reversal of typical cichlid sex roles: breeding females are spectacularly coloured in blue, red, and violet, while males are comparatively dull and brown. This makes reliable sexing easy and the fish endlessly fascinating to observe.

The species is a cavity-spawner that requires very soft, very acidic water — pH 5.5–6.2, low conductivity, high tannin content — to truly thrive and breed. Blackwater aquarium preparation with peat filtration or regular Indian almond leaf additions is strongly recommended. The species is sensitive to poor water quality and will not tolerate alkaline or hard tap water long-term.

Keep as a pair in a species tank or with very peaceful dither fish. N. transvestitus is territorial during breeding and can be surprisingly assertive for such a small fish, particularly the female.

Water: 24–27°C, pH 5.5–6.2, very soft (GH 1–6, KH 0–3); blackwater conditions essential — use peat or Indian almond leaves. Tank: 60 L minimum; dim lighting, leaf litter, fine sand, and flat rock crevices for spawning. Feeding: Small live or frozen foods strongly preferred — baby brine shrimp, daphnia, micro-worms; will accept small pellets once settled. Breeding: Cave-spawner; the more colourful female initiates courtship — both parents guard fry. Compatibility: Species tank recommended; only the most peaceful, unobtrusive dither fish if mixed.