ID plz

[supernareg]

i see these things growing on my SPS... only seen about 4 of them, took 2 of them out, now i see 3. they're hard, and they were stuck on the sps. i had to really yank them with tweezers. they ahve hard shells

 

[gregm5]

can't really tell by the picture but it's probably just a barnacle if it has a hard shell