ID please

[atjw]

Just found this in my tank, at 1st glance presumed it was part of my star polyps that had got blown off around the tank but just realised after watching it thats its actually moving slowly around the tank.
Is it an Anemone of some sort?
Good or bad?

 

[smh254]

Need a pic but u can check here
http://www.lionfishlair.com/hitchhikers-guide/

 

[atjw]

Sorry thought it uploaded but clearly not [emoji23]

 

[atjw]

 

[smh254]

Nudibranch maybe if so I would remove

 

[atjw]

Thats what i thought at first as had them a few years ago but its definitely not that, its got a round base like a mushroom/toadstool & a hexagon shaped front disc where the green flowery looking bits are.