Heard you have to wash and squeeze them out once in a while .. like a sponge.
Mmm, you do! Just squeeze them gently a couple of times in old tank water during a water change and it'll do the trick. If they don't get much current they'll need to be manually rolled about, too. But this doesn't seem to be a problem stemming from either of those points.
Hopefully somebody here has some experience with this type of growth!
i think these require high light or direct sunlight. i never had success with it in my tank, i have medium strong LED 7000k. when i put it in direct sunlight directly in front of the window, it floats and makes bubbles. i don't need to form it. at night it sinks and stays still. pretty neat.