MANASSIRI K / SHUTTERSTOCKWith their whimsical appearance, ubiquity, and gushing
claims of their virtues by aquarium plant vendors,
Marimo Balls may seem to be just another kitschy
horticultural fad akin to “Lucky Bamboo” (Dracaena
braunii), but these living aquatic organisms represent
both a unique natural phenomenon and a distinct branch
on the tree of life. Despite the rather exacting parameters
for their development and persistence in nature, Marimo
Balls are relatively undemanding in captive care. With
a minimum of attention they can live for years as
cheerful, hardy, emerald-green globes in low-tech planted
bowls, but they may also find a place in more ambitious
aquascape projects. The Marimo Ball is a worthy denizen
of a planted aquatic setup.Classification: alga, not moss
Some confusion about origins and pedigree has followed
the Marimo Ball as it has rolled its way through the
aquarium hobby like an eyeless, legless, headless Muppet.
Sometimes called “moss balls,” Marimo Balls are, in fact,
perfect orbs comprised of densely packed filaments of an
alga, Aegagropila linnaei (Family Cladophoraceae). Among
other unique characteristics, this mainly freshwater spe-
cies—it also grows in brackish Baltic Sea bays—is classi-
fied with the Cladophorales, which, together with other
groups, comprise the Ulvophyceae. A few of these mainly
marine algae, such as Caulerpa, Codium, and Ulva, aredesirable (or sometimes weedy) additions to reef aquari-
um systems. One or more species of marine Cladophora,
unpalatable for most aquarium herbivores, can also grow
as serious pests in reef aquariums.
For a time, A. linnaei was classified as a Cladophora
(C. aegagropila), but it was subsequently restored to its
first name as described by German botanist Friedrich
Traugott Kützing in 1843. It remains the sole member
of its genus, distinguished from Cladophora by morpho-
logical characters and molecular evidence. The genus
name is from the Greek for “goat hair” owing to its
rough, hairy texture (incidentally, the scientific name
for the domesticated goat is Capra aegagrus hircus), while
the species name honors Carl Linnaeus. The Japanese
common name, Marimo, was coined in 1898 by bota-
nist Tatsuhiko Kawakami as a simple compound noun
combining mari (toy ball) and mo (alga).In the wild
Marimo Balls occur in special environments in nature.
All known locations are in previously glaciated areas of
the Northern Hemisphere, although the habitats are less
like the oligotrophic Canadian Shield lakes (very clear
water, slightly acid pH, limited nutrients) that might
come to mind. Most are better characterized as naturally
oligomesotrophic with more available nutrients, includ-
ing calcium, and neutral to moderately basic pH. TheyAMAZONAS
Mini Marimo Balls, currently enjoying a wave of
popularity as windowsill and desktop water-garden
“pets.” The name “Marimo” is a Japanese label
meaning “algal toy ball.”