I started with a couple on a small rock 8 inches from anything. 2 years later, the entire tank was covered. I would really think twice about adding them on purpose. I thought the same thing, keep them separated like GSP..I just recently read a thread about the spawning with pics of the eggs.
Pesticides required to get rid of them....

My sale just fell through.. Thanks guys! :-(

I can paypal you a dime..my way of apologizing