Help ID these - looks like a snail, but doesn't move?

[Tri2Spike]

Can somebody help ID these? And are they good or bad?

Got 4 or 5 of these in my tank. It looks like some type of snail to me, but they don't move at all. They are about 1/2 inch in diameter. I haven't introduced anything into my tank in about 9 months, and these guys appeared about a month ago.

The 2 orange/brown blobs in the middle of this picture:

Thanks!

 

[samnaz]

Maybe vermetid snails.

 

[vetteguy53081]

looks like tubes of spinoid worms or segmented worms of the polychaetes grouping of tube worms

 

[KJ]

Vermetid snails.

 

[Tri2Spike]

Thanks all, I will remove them.