Dead Man's Fingers

Codium fragile

Also known as Codium, Sea Fingers, Green Sea Fingers, Green Fleece, Sponge Seaweed

SaltwaterMacroalgaeCuttings

Dead Man's Fingers (Codium fragile) — Coughdrop12 · CC BY-SA 4.0

Care at a glance

Light: Medium light
CO2: No CO₂ needed
Temperature: 68–81°F; 20–27°C
Max height: 9.8 in; 25 cm

Growth rate: Medium
Placement: Background
Type: Macroalgae
pH: 8.0–8.4
Spread: 9.8 in (25 cm)
Nutrient uptake: Water column
Growth region: Submersed
Difficulty: Medium
Family: Codiaceae
Origin: Temperate and subtropical coasts, native to the northwest Pacific around Japan and Korea, now widely naturalized

Overview

Dead Man's Fingers is a dark green display macroalga for a temperate or moderately cool marine tank. It is rated medium in difficulty.

Did you know

Dead Man's Fingers is also called oyster thief. Pockets of oxygen trapped in its spongy tissue can lift an attached oyster or mussel off the seabed and float it away.

Caring for Dead Man's Fingers

Attach Dead Man's Fingers to rock rather than planting it in sand. It wants medium light, moderate to strong flow and no added CO2. It feeds from the water column and exports nutrients as it grows.

It prefers the cooler end of the marine range, 68 to 81°F (20 to 27°C), and gets unhappy in very warm tanks. Keep the pH at 8 to 8.4.

It grows at a steadier pace than Caulerpa, to about 10 in (25 cm), and does not carry the same overnight crash risk. That makes it a calmer choice for a display refugium, where its branches also shelter pods. Tangs and other herbivores can graze it.

Good to know

Dead Man's Fingers has a spongy, felt-like build. Its body is a woven mesh of coenocytic filaments, or siphons, whose swollen tips, the utricles, pack together into the solid-looking finger surface. It holds on with a basal holdfast rather than roots. It is a notorious biological invader outside its native range.

In the wild

Dead Man's Fingers grows on cooler temperate and subtropical rocky coasts, native to the northwest Pacific around Japan and Korea. It forms branching, cylindrical, spongy fingers that fork again and again. It attaches to rock and shells in the low intertidal and shallow subtidal zones, and it has now spread worldwide.