The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
That's a type of Macroalgae. I can't remember the name, but have seen them in other threads, and they were an invasive species. You would be best served to remove them before they can spread.
Neomeris sp. Not really thought to be aggressive but it can spread. I have seen it in many of my tanks. I usually pick it if a see a few stalks growing and it will keep it at bay i have found pretty easily.