White smooth material on LR

[Charlie]

My 46 gal FOWLR is about 1 month old. The LR has a partial covering (in some spots) that looks like white enamal paint. I believe that it is spreading. It is perfectly contoured to the rock like coraline algea. Too bad it's not purple.

Any guesses as to what this is?

 

[roka64]

Without a pic, I would tend to guess a sponge of some sort.

 

[lando]

a pic would help. my guess is coraline algae.