Aegagropila linnaei, (formerly Cladophora Aegargropila)
aka Marimo balls, algae balls, moss balls
Known in Japan as “Marimo balls”, it is a species of filamentous green algae (Chlorophyta) found in a number of lakes in the northern hemisphere: in Iceland, Scotland, Japan and Estonia. It is a protected species in both Iceland and Japan where it is also designated as a national treasure. There are three growth forms. The epilithic form is usually found growing on the shaded side of rocks. Free-floating filament is another form and it often forms a carpet on the lake bottom. The third growth form is the lake ball form that has made the plant famous. The algal grows into large balls of densely packed algal filaments. Larger size balls are hollow in the center. They do not form any sort of seed or flower.
These unique plants are imported from the northern Estonia-Baltic region. In Japan filaments are rolled by hand and sold in stores, (the lake balls are prohibited). Marimo balls ideally should be kept in cold water. Temperatures above 78F should be avoided. They have evolved under very low light conditions and are highly suitable for low tech aquariums. High intensity lighting should be avoided and adding C02 is not needed. They will grow healthy under ambient room light in a bowl of water. The most critical thing is keeping the water well oxygenated and fresh with frequent water changes. You should not allow sediment to build up on the balls. This may be prevented by holding the balls under running cold water to clean them and wring out any accumulated dirt. Failure to do this may cause brown or black spots. Such spots can be often eliminated with proper care. During extreme hot weather the balls may be stored in a refrigerator, but will not survive freezing.
Growth is extremely slow and contrary to aquarium myths they cannot out-compete other forms of algae or other plant species for nutrients. Other faster growing hair or filament algae can grow on top of a Marimo ball just as easily as it would on a rock or piece of wood.
Marimo balls have become a favorite for freshwater shrimp keepers. They provide the perfect medium for shrimp to forage on for bio film and micro- organisms.
Marimo Q and A
Q. Can I flatten out the ball and have it continue to grow?
A. Yes, but it should be kept clean
Q. Will it adhere to wood or rock?
Q. Will algae eating fish and shrimp eat it?
Q. Will it take over my tank?
A. No. It grows extremely slowly