ID of growth on a coral

[TiggrReefer]

What is this white-ish growth on the bottom of this piece of coral?
Good?
Bad?
Try to remove??

 

[ISpeakForTheSeas]

My best guess would be a sponge, as it looks too large to be mesenterial filaments, but I can't tell for sure from the pic - sorry.

If it is a sponge and the coral isn't acting unusually unhappy in the areas close to it, then it's most likely harmless.