i doubt you would end up with a mat of algae if you just put an aerator below a marimo ball. i first grew a more aggressive type of hair algae into a mat and used it as a matrix for the shredded marimo algae to grow in. this allowed me to infuse the marimo type clado into the mat without ending up with a bunch of tiny marimo balls. i think there is another type of algae in there as well, but i have lacked the time and motivation to pull out my microscope for verification. ill probably get to that soon.
growing the algae into a mat involves using a long stranded fast growing clado to form a thin sheet and then using a shorter algae to cause it to form a dense mat. it ends up having the feel of rough wool. if i wanted to, i could cut it and make cloth out of it.
since there are two different types of algae, i should be able to modify its environment somehow so that the faster long stranded algae dies off, leaving the attractive short fluffy stuff behind. the marimo clado can survive with very low light, so i may just try scaping with the algae pads and turning the lights down low and reduce photoperiod long enough to kill off all the faster growing stuff. that would leave me with just aquascaped marimo that is attached to driftwood and such.
marimo balls are strange things, they consist of an algae that grows incredibly slowly when in the form of a ball, but much faster when its shredded into individual strands. hopefully, i can come up with a way to quickly create an entire tank decorated with neatly placed and well behaved algae.
that idea kinda stomps on the idea of algae being a nuissance in an aquarium...
then again, so does a marimo ball.