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?

 

[rcdude1990]

is it outside of the tank?
if so then it is salt recidue or salt creep, jus rub ur finger hard over it, but wen u say decorations then i have no idea but if it is outside of the tank then it is saltcreep

 

[spanko]

Probably dead or bleached coralline aglae.