Well I have had it show up in my tanks and typically not become invasive but I can see the potential to become invasive if nutrient levels are elevated in the tank. BTW I had not added Chaeto to my system either and there are a couple different types of Chaeto. My thinking is that it comes in on frags and under the right conditions it will take hold.
So of course nutrient control is important. A Purple Sea Urchin would probably eat it but I can not say for sure. Might want to reach out to ReefCleaners.org and see if John knows of a critter that might take care of the issue.
Good to know. Yea Ive been trying to elevate my nitrates from zero with potassium nitrate, which only contributes to the algae I guess. Thanks for the response.