ID Please

[darrinf15e]

I have no idea what the white sponge looking thing with spines is. It appeared on my live rock 2 months ago and has been growing slowly. For size comparison, a Firefish can be seen to the left. Sorry if the focus is not great, I need a better camera. It is Fiji rock and has quite an abundance of life including sea squirts, q-tip sponges, many various worms, random small bugs, and limpets.

Is the spiny fuzzy thing good to have, a pest, or a straight up killer?

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[Devilishturtles]

I believe that is just another species of sponge. I have a few in my tank too. The spike things are to catch food I think.

 

[smn723]

looks almost like a foraminiferan...tried to find a site on this... this is the best i could find:
http://home2.pacific.net.ph/~sweetyummy42/hitchodds.html

 

[melosu58]

Moved to the ID forum.

 

[Fluff]

I agree with Devilish, it looks like a ball sponge. Nothing to worry about.