Ok I researched that they move up and down to the surface and the bottom to receive the proper lighting for photosynthesis. Also a little fact is that you can actually cut them in half to form smaller little balls - though I wouldn't. - It doesn't hurt them and you can also roll them out into a lawn like surface. Some might say no, but I have done my research well, and I promised someone -I won't say who- that I would check and 're check my facts before posting.Another little thing is that since they are packed with nutrition, it's perfectly safe for your betta to nibble on it,( Though some might not. ) and will give your betta extra nutrition.
really hope this helped!!!!!!