THey send out plants or shoot in many directions. Then those satelitte plants do the same thing, so the mass grows extremely fast if left unchecked. They are fairly easy to deal with, if you are committed to do so and have the time. I like to keep the new ones to filter and toss the older clogged ones who have done thier job. They will even start eating muck off the bottom if they can reach it, and pull in everything from algae to minerals. Some fish nibble on thier roots.
