Hello, So I have a small NTF system I built and I am getting some odd white powder substance built up. This system is new and not in use yet. I have not added anything to the water yet. I just built the system and wanted to make sure no leak would develop over time, before I put live plants in. After a few days of letting the system run I get this white substance built up on the top of the compressed clay pellets. I am trying to identify what the substance is and if I need to worry about it being there? Image 1: Image 2: Any help would be great! Cheers!