small white hard substance

[min12512]

recently ive seen a lot a small hard white substance on my decorations and on my aquarium. i cant use a brush to brush them away they are too hard. i have to use a scrape to scrape them off but really dont want to damage anything. does anyone know what this hard white substance is? and how to get rid of it?

 

[rbrockm1]

i had the same thing. i payed no attention to them and they are almost gone. i don't know what they were but there pretty much gone now