Hello everyone! Just trying to see if someone can help me identify what the white scale like substance is in the picture attached. It’s basically all in my sump and on most of my equipment. Is not easy to get off and has to be basically scrapped off. I have researched online but have not found anything. It may be something typical but I am just not familiar with it. Trying to figure out what it is and what causes it. Thanks in advance for any help. My tank has been up about four years and this started about an year or so ago.

