well from the research i could gather it seems that marimo grows in a ball because of its natural habitat. Water currents keep it rolled and the ball shape allows the ball to receive light and maximize surface area for receiving nutrients.
I keep finding references that there are 2 types of marimo. "fake" and real. However, i am seeing conflicting information about which characteristics belong to which type. From what i could find it seems both marimos can grow opened up and flat since the shape was caused by environmental factors and not a structural growth. However, "real" marimo is supposed to have a spiralish structure which helps it maximize growth in all directions to help it stay roundish, whereas fake marimo grows with a more fuzzy structure, kinda like BBA but green. Both clados, due to their fine stringish structure, will pearl, which causes them to float and become susceptible to currents moving them around, which would lead me to believe that the plant would not easily anchor itself since it doesnt actually have a lot of opportunities to in nature.
On many accounts where aquarists complain about marimo balls breaking into an outbreak really sounds more like algae introduced to aquaria because it was growing on the ball already. Both types of clado balls are "supposed" to be slow growers and usually inedible by other tank inhabitants, INCLUDING amano shrimp. However, outbreaks of fuzz algae, thread algae, etc are all containable by amano shrimp.
Personally, i dont care which type of clado i have as my ball, i really want a soft lawnish growth. I already broke up, what i suspect to be, fake marimo, but it like to float ~1-2mm over the gravel and my shrimp have started using it as a cave, which means i dont get to see them anymore. Now to complete the aquascape, i need the marimo to fuse with the gravel, but from various forums online, it seems to be nearly undoable and the only image of it that i could find it on the substrate was from that picture i posted. Im wondering if the algae was one that could only truely attach to itself structurally unless it grows INTO something else, ie: driftwood due to woods porous nature or if it can grow ON something, ie: rocks.
in my quest to find the latter, which would tell me it could work on gravel, i realized i rarely found any marimo on rock, as the ones i saw were all tucked into cracks or anchored between 2 rocks. even marimo that were shaped like rock: Tropical Fish News Tank Journals & Photo Album
(one of the posts had marimo in the shape of a rock) was actually just marimo torn up to look like the shape of a rock (you can see space between the bottom of the "rock" and the gravel.)
The more i look into this, the more it seems like the ball grows into things and doesnt actually attach to things. Im still hoping someone posts and tells me its all possible though since that would make me the happiest aquarist ever.