Marimo moss ball

Aegagropila linnaei

Also known as Marimo, Moss ball, Lake ball, Cladophora ball, Cladophora aegagropila

FreshwaterBrackishMossDivision

Marimo moss ball (Aegagropila linnaei) — コムケ at Japanese Wikipedia · CC BY-SA 3.0

Care at a glance

Light: Low light
CO2: No CO₂ needed
Temperature: 39–82°F; 4–28°C
Max height: 3.9 in; 10 cm

Growth rate: Slow
Placement: Foreground
Type: Moss
pH: 6.0–8.5
Hardness: 2–18 dGH
Spread: 3.9 in (10 cm)
Nutrient uptake: Water column
Growth region: Submersed
Difficulty: Beginner
Family: Pithophoraceae
Origin: Lakes and slow rivers of Northern Europe, Japan, and scattered cool temperate regions (notably Lake Akan, Japan and Lake Myvatn, Iceland)

Overview

Marimo moss ball is about the easiest "plant" you can keep, and it is a beginner's choice for the front of the tank. It needs almost no care beyond the occasional roll.

Did you know

Marimo balls float and sink on a daily rhythm. During the day, photosynthesis traps tiny oxygen bubbles in the velvety surface and lifts them toward the light. They settle back down at night as the bubbles escape.

Caring for marimo moss ball

Set the ball loose on the substrate in the foreground or midground, with no planting or attaching. Roll it gently now and then so every side gets light and the round shape holds. Rolling also clears debris and detritus from the underside.

Marimo moss ball does well in low light with no CO2, and it grows in freshwater or brackish tanks. It takes its nutrients from the water column, so a liquid fertilizer feeds it, though it gets by with no dosing at all. It handles 39 to 82°F (4 to 28°C) but prefers cooler water, since heat near the top of that range can brown it.

Growth is extremely slow, a few millimeters a year, so the ball stays put and never needs trimming. To make more, divide a large ball into smaller pieces.

Good to know

Marimo moss ball, Aegagropila linnaei, is not a moss or even a plant. It is a filamentous green alga in the order Cladophorales and the family Pithophoraceae. The ball is a colony of branching filaments radiating from the center. The same alga also grows as free filaments or flat mats on rocks in the wild. Shops also sell it as Cladophora ball or lake ball.

In the wild

Marimo is native to cool, clear lakes and slow rivers across Northern Europe and Japan, with scattered populations elsewhere. The spherical lake ball form develops in only a few lakes, where gentle wave action rolls loose filaments into velvety green balls. It is strictly protected and considered endangered at its best-known sites, including Lake Akan in Japan and Lake Myvatn in Iceland.