---
title: Half-and-half Chromis (Pycnochromis iomelas)
scientific_name: Pycnochromis iomelas
common_name: Half-and-half Chromis
taxon: Pomacentridae
conservation_status: LC - Least Concern
published: 2023-12-30T21:28:21.395Z
updated: 2026-08-15T14:15:49.180Z
tags: Half-and-half Chromis, Pycnochromis iomelas, Pomacentridae, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/fishes/bony-fishes/pomacentridae/half-and-half-chromis
---

# Half-and-half Chromis (*Pycnochromis iomelas*)

## Quick facts

- **Group:** Pomacentridae (*Pomacentridae*)
- **Size:** up to 8 cm
- **Depth:** 3-35 m
- **Diet:** Carnivore
- **Activity:** Diurnal
- **Rarity:** Uncommon
- **Habitat:** Reef slopes and drop-offs with current
- **Reproduction:** Egg layer, Gonochoric
- **Conservation status:** LC - Least Concern

## How to recognise it

- front half black, rear half and tail abruptly white
- the division is a clean vertical line, not a gradient
- in small groups in midwater off the slope
- length up to 8 cm

Black in front, white behind, split down the middle by a line so clean it looks painted. Eight centimeters (3 in) of fish that is hard to misidentify and hard to expose properly.

Sharp two-tone patterns like this are common in small reef fish and their function is argued over. The most likely job is confusing a predator's aim: at speed, in a group, the pattern breaks up where one fish ends and the next begins, and a strike aimed at what looks like a fish lands between two of them.

It feeds on plankton in open water off the slope, like the rest of its genus - facing into the current, taking one animal at a time, and dropping back to the reef when something large arrives.

The genus name changed recently: the chromis were split, and a number of species moved to *Pycnochromis*, so older books and photo captions still file this one under *Chromis*.

## Also known as

- **English:** Half and Half Chromis, Pacific Half-and-half Chromis, Half-and-half Chromis
- **French:** Chromis moitié-moitié
- **Portuguese:** Donzela-bicolor-do-Pacífico
- **Czech:** sapín hnědobílý
- **Russian:** Двухцветный хромис
- **CA:** Castanyoleta bicolor del Pacífic
- **DA:** Kontrast-jomfrufisk
- **TAH:** 'Atoti

## Scientific synonyms

- *Chromis iomelas* Jordan & Seale, 1906
- *Chromis isomelas* Jordan & Seale, 1906

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/fishes/bony-fishes/pomacentridae/half-and-half-chromis)*
*Updated: August 15, 2026*