Platys Biting On Decoration

[Rox]

I have a discosoma decoration in the center of my tank (link) and after a while it's grown some white spots on it, which the platys will nibble on sometimes. I understand that platys will eat algae but I just wanted to know if I should ever wash this or not, and how often.

 

[OldMan47]

White stuff on that decoration is most likely a colony of some kind of bacteria or a similar microscopic growth. Since platies graze most of the time, it is not at all unusual to seem them find and focus on any growth at all.