Did you call? Lol
That is a cool article,I did already know that they are algae,though I know that they will move around the tank if they aren't getting enough lights or nutrients. I really like he way they look in a nice planted setup.
Here is a little thing I found on them, I did not write this. I just found it
Bio: Marimo/Moss balls are a very interesting plant indeed. Compact balls of special moss, these plants take on a life of their own and sometimes move about the tank and up the sides without being touched. The can range from very small balls to very large, fist-sized balls of moss. They are fantastic tank cleaners and help keep the tank naturally filtered.
Ideal Temp: 70-80’F (Some believe this plant fares best in cooler water, 77’F and less)
Substrate/Rooting?: This plant shouldn’t be buried or tethered to anything. Allow them to plop into place, and if they move, just move them back. You may find them floating, climbing the sides of the tank, or hiding amidst other plants.
Ideal Spot in Tank/Light: Place these plants where you can enjoy them. They are very quirky and interesting, and should be on display. This plant does very well in low light, but can do well in moderate light as well.
Fertilization: Fertilization helps this plant grow. Growth is usually slow. Use: Liquid fertilizers, if already in the tank, root tabs.
Special: On occasion, pick up your moss ball and give it a gentle squeeze to remove the cruds it picks up while on its travels in your tank. Do not be too rough with it, though! Dunk it gently a few times in water to remove debris, and then add back to the tank with the old bottom facing up, so it won’t yellow. This plant can be attached to objects when pulled apart, if desired. However, there are better options for mosses that are much cheaper, like Java moss. It’s best to leave these guys as balls.