it is possible if you dont buy a true marimo. sometimes sellers can be sneaky and use another type id clado algae . one which doesnt stay nice and compact in you tank.... but rather spreads and grows where its unwanted
Wow, I looked up clado algae and that's an awful trick for stores to play!
Marimo moss is actually a type of algae itself. It's supposed to compete with the bad algaes that you don't want by using the same minerals and vitamins or whatever. But I have seen algae grow around the tops of tanks whereas the marimo stayed at the bottom.
In any case, marimo moss balls should not be bought for the purpose of controlling algae and doing less water changes. :) Hope this answers your q.