To late.Its already infected your tank.
In a month,the tank will be completely full of kenya weeds.They'll be growing out the top.Dropping branches all over the floor.You'll try to rip em out,but they'll attach to your hands and even you will become a kenya weed.
Take that rock out of the tank.Then have the air force drop some napalm on it.Once that fire is out,have North Korea strap it the nose of a ICBM they are about to test fire.Then find the pieces and have NASA shoot them into the sun on a rocket.
All that still wont guarantee the death of the kenya,but at least it'll get out of your tank.Hopefully.:Cheers: