ID please?

[Haus]

not sure if these are something to be worried about or not, but I noticed a few of these on my live rock over the last week and now I see a ton of them in my hang-on fuge (that's what this picture is from). They're small-a half centimeter at most.
Can anybody ID them?
Are they a potential problem?

Thanks in advance!

 

[Tyler]

The white things? Pineapple sponges; harmless filter feeders. Nothing but a sign your tank is maturing, you may have a bloom of them but they will die down on their own.


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[Haus]

Thanks! That's a relief