Plant ID

[simmons797]

Can someone help me ID this plant. I have it growing in two tanks on rock that came from different places at different times so I'm guessing it's something fairly common. It's growing on the rock (I think it's fiji rock) and hasn't spread to any other places in the tank. When it gets several inches long it starts getting the balls (seeds?) like you see in the picture, when this happens I usually snap it off near the base and let it grow back in. Thanks in advance for any help.

 

[Random Aquarist]

That would be Sargassum aka kelp. Once again, some people like the look of it and keep it, and others don't. In other words, it's not a pest algae.