Please help ID

[Reef2187]

Hello guys, I have these 3 corals in my system. I believe all 3 are the same. Can anyone tell me what they are? Are they aggressive? They have grown quickly in my system. As you can see in the last picture, one is getting very close to my Acan. I want to turn the area into an scan garden. Should I remove it for it not to invade my Acans? And if so, would a local fish store have any interest in it? Thanks in advance.

 

[BMW540]

Hydnophora. I'd move it away from the acans as it has a fairly potent sting.

 

[Reef2187]

Thank you