Sorry this plant Marimo Moss Balls is now banned in the USA. It is not legally for sale anywhere as of Mar 2021.
At first it was thought that Marino was extremely slow growing. 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 (I would avoid doing this in my tanks) or by providing more nutrients. It ranks among the strangest plant on Earth and has been granted the status of National Treasure in Japan.