What are these?

[pzunker]

I thought at first that these were aiptasia but the larger they get the less they look like those. Could they be some sort of soft coral?

 

[PsychoticBeauty]

Ball-Tipped Anemone. In most cases these are harmless, but definitely keep your eye on them.

 

[pzunker]

Thanks. So they can be bad then? I don't have any corals. What should I watch out for?

 

[zeemofree]

Thanks. So they can be bad then? I don't have any corals. What should I watch out for?

it will travel, and can poison your tank if chopped up with a powerhead. Cool little nem

 

[AlSimmons]

Thanks. So they can be bad then? I don't have any corals. What should I watch out for?

The link below might help.

http://www.advancedaquarist.com/2002/10/inverts