Cladophora aegagropila,

The Lake Balls

by Martin Kelly.

At our June club meeting, Malcolm Goss mentioned the green algae balls, (Cladophora aegagropila), that have recently appeared on the market and consequently the showbench. I decided to do some investigation into these strange plants and discovered quite a lot of information.

Cladophora balls were first discovered in Lake Zeller, Austria in 1824 by Dr, Anton E Sauter, a physician and botanist They were named CIadophora aegagropila and they belong to the Cladophora sauteri group. CIadophora means 'branched plant'. aegagropila means 'lake ball' and sauteri is derived from Dr. Sauter's name.

Lake balls were subsequently found to exist in the United Kingdom, Russia, Iceland Sweden and other countries.

Lake balls have a green velvet like appearance and have been known to grow to about 30cm in diameter. At one time it was thought that Cladophora was extremely slow growing, taking between 150 and 200 years to reach the size of a tennis ball. Recent studies however suggest that the slow growth rate in more recent time is due to poor water conditions, It has also been found that the growth rate can be improved by mixing sea water with the lake water. In common with most plants, Cladophora aegagropiIa obtains nourishment by absorbing sunlight using the process of photosynthesis.

The plants must remain in positions that receive plenty of sunlight otherwise they wilt start to die. Fortunately the plants are able to move around by using the undercurrents of the lake, which allows them to swap places with plants in the deeper areas of the lake, This process of rotation allows all the plants to photosynthesise and therefore ensures their survival. It has been reported that the plant has the ability to float or sink, in order to position itself depending on the brightness of the sunlight. CIadophora aegagropila tends to grow in large groups in the shallower parts of the lake.

They can grow so densely that other plant life can be totally obscured. Another benefit of being spherical is that when silt and other fine debris collects on the uppermost surface of the plant, gravity causes it to naturally rotate with the weight and the debris will fall off.

Today, Cladophora balls can be found in Lake Myvatn in northern Iceland, although there is far more information relating to the balls found in lake Akan in Japan.

Northern Iceland

Lake Myvatn is a 37 sq. km lake in the volcanic region of Iceland. The most abundant fish in the lake is the Three Spined Stickleback, with other inhabitants including the Brown Trout and the Arctic Char The whole area has been declared a wetland of international importance and is protected by law.

The lake is constantly monitored (since 1992), by use of aerial photography to follow changes in the distribution of the Cladophora mat on the bottom of the south basin.


Lake Akan is the most commonly known lake containing Cladophora balls, but they can also be found in Lakes Shiranitoro, Toro, Kawaguchi and Sai. All these lakes are in The Iloklaido district of Japan.

Local mythology surrounding these balls tells the story of a young man and young woman who are said to have drowned in the lake, their hearts turning into CIadophora balls. The survival of the balls in Japan has been under threat on more than one occasion.

The use of Lake Akan to transport timber caused many a plant to die. As the timber floated in the lake whilst waiting to be transported, it blocked the vital sunlight that the plants require.

Between 1945 and 1954, water powered electrical generators caused a drop in the lake's water level, leaving many plants exposed to the open air, and nearly eradicating the population

The CIadophora balls, or 'Marimo' as the Japanese call them, were declared a Japanese Natural Treasure in 1921, and then in 1952 they became a special Japanese Natural Treasure.

This special status was a real problem for the plant as many people wished to own one and grand scale theft of the plant threatened its survival. CIadophora balls are current]y so popular in Japan that they are now protected plants. It is said that plants of other non-ball forming species are rolled by hand into balls and sold as true Marimo.

This raises the question, what really are these plants that are turning up in our shops and on our showbenches? If they truly, are CIadophora aegagropila. which are supposedly protected in Iceland and Japan. then where do they come from? It they're not, they must be of the hand rolled variety, in which case the aquarist should be wary.

I'll leave you to make your own decisions.