Clearish growth on live rock?

[Shane1]

Hey all I noticed two of these in my tank. This is the one I can get the best pic of. It's the cloudy white ball looking thing near the upper right corner of the magnet cleaner. Any help would be appreciated.

 

[Salty B]

One of many sponges that will come and go. Not harmful at all. I had one grow to about the size of a golf ball. After being there for 6 months it vanished completely in about a week. They come in many colors too.

 

[Shane1]

Thanks very much for the info!