White sponge or cotton ?

[Payedjay]

Now this grows on coral I scrap off how do I get rid of it completely thanks

 

[marrone]

They look like Q-Tip or pinapple sponges. They're harmless and a good thing to see in the tank. It's best to just leave them alone.

 

[piranhapat]

If your noticing alot all of sudden. They can multiple if you have high silicates. If you only see a few it's ok. They can become a problem because they can be everywhere in your skimmer and pumps. Especially if they bloom. Easy way to get rid of them you can remove silicates with silicates media remover. Only if you have alot. They are not hameful to your tank. Sponges are a good thing they say. I don't like them. Just me.