White multiplying particles in new tank

Hi everyone, I had an incident with a strange white substance about a year ago in my tanks. It started in one and spread to others. I posted about it before in another thread. It was like a white particle snow that would multiply like crazy and attach itself to all surfaces even My fish. I bleached everything multiple times and used hydrogen peroxide treatments. It always seemed to come back so I put my tanks away and let them be to dry out and not do anything with them for awhile. I recently just refilled the tank it all started in with plain water. I’m trying to see if the stuff will come back. Is it normal to have white particles at the bottom of a tank that’s been sitting for a few days with no added chemicals/bacteria or a filter just the tank and water. And if not does anyone know what that stuff might be and how I can fix this?