Curious Newbie

I just recently got back into the hobby of aquatics with a 5 gallon tank housing shrimp, snails, and a couple guppies, and a 3 gallon nano cube cycling for a betta. I have floating plants, like Water Lettuce and Duckweed, and some Christmas moss for my incoming shrimplets but I've absolutely always wanted a Marimo. I got to thinking, with having these tanks now, maybe I could finally have one or two. Could a few small ones or a single bigger one be kept in either tank, specifically the 5 gallon at least? Or are they better in their own container?