What the heck is this?

[Fibinotchi]

It resembles a hydroid but I am not sure, I have no idea what it could be, but there is another larger one that has about 20+ tentacles in an area where I can see at night with a flashlight but can't get a picture. This is very small, about the size around of a ball point pen tip or slightly larger than that. The one on the upper right is what the one on the left looked like until yesterday. The tentacles have little round white colored balls at the tip and they radiate around the center in a circle when it is bigger.

 

[dalston]

It's very hard to see but I'm going to guess it's a pseudocorynactis.

 

[Fibinotchi]

Thank you, that is exactly what it is. I don't know why I couldn't find it anywhere, no one seems to show it as a pest, but I don't think I want it in my tank since it is dangerous to small fish and inverts.

 

[dalston]

I'm not too sure that it's dangerous to fish and inverts...It's a member of the corallimorph family (mushroom). The biggest i've ever seen them is nickel sized. I have a few in my 12 nano with plenty of inverts and nano gobies.