Any ideas?

[KLehman72]

I discovered this growing on my live rock...kinda cottony looking. My Coral Banded Shrimp decided to stick his antenna in the shot...

 

[hackteck]

looks like a sponge

 

[KLehman72]

A sponge...good or bad?

 

[Bonz]

If its new lr that you bought, chances the sponge will die off if it was in the air during transportation( air blocks the cells). They need movement because they eat detritus and are beneficial to a system. Sometimes fish eat it and help it spread.

 

[Bnortz]

i had that on my LR when i first got it. just a harmless sponge