What is this???

[AR_Clint]

Found this on my skimmer pump. I've also found a few throughout the tank. It's transparent white in color. The picture actually has 2 in it, but one is behind the other and sticks out to the right. Anyway, can anyone tell me what this is and if I should be concerned?

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[arts007]

appears to be whats referred to as a pineapple sponge, harmless filter feeders

 

[weaselslucks]

I forgot the name but its a harmless filter feeding sponge

 

[Andrew]

Just a Scypha sponge. Harmless and are found in most tanks.