---
title: Weedy Cardinalfish (Foa fo)
scientific_name: Foa fo
common_name: Weedy Cardinalfish
taxon: Cardinals
conservation_status: LC - Least Concern
published: 2024-11-08T15:54:25.509Z
updated: 2026-08-19T09:08:36.347Z
tags: Weedy Cardinalfish, Foa fo, Cardinals, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/fishes/bony-fishes/cardinals/weedy-cardinalfish
---

# Weedy Cardinalfish (*Foa fo*)

## Quick facts

- **Group:** Cardinals (*Apogonidae*)
- **Size:** 3.5 cm
- **Depth:** 1-82 m
- **Diet:** Carnivore
- **Activity:** Nocturnal
- **Rarity:** Uncommon
- **Habitat:** Seagrass, weed and rubble in sheltered shallows and on deeper slopes
- **Reproduction:** Mouthbrooder
- **Conservation status:** LC - Least Concern

## How to recognise it

- under four centimeters, mottled brown and cream
- no stripes or spots in any regular arrangement
- in weed and seagrass rather than on coral
- up to 3.5 cm

Three and a half centimeters of fish recorded from one meter down to eighty-two.

That is a strange span for an animal this size. Small fish generally have narrow ranges, because the smaller you are the more the physical conditions matter and the less able you are to move between them. A range like this usually means one of two things: the species is genuinely tolerant of everything from surge-washed weed beds to dark deep slopes, or several different animals have been recorded under one name.

The second possibility is not idle. This is a tiny, mottled, unremarkable fish that lives in seagrass and weed, and separating it from its relatives takes counting fin rays under a lens. Groups like this are exactly where undescribed species hide, and the wide recorded ranges are often the first clue that something needs splitting.

Until somebody does the work, the honest position is that a small brown cardinalfish in weed anywhere between the shallows and eighty meters may be this species or may be its unnamed neighbor.

It hides in vegetation by day, feeds on small crustaceans at night, and the male carries the eggs.

## Scientific synonyms

- *Apogonichthys fo* (Jordan & Seale, 1905)

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/fishes/bony-fishes/cardinals/weedy-cardinalfish)*
*Updated: August 19, 2026*