White stuff floating in toilet tank?

[Frelon]

If they are floating gather the bits up with a tissue from the surface of the water and completely remove them. If they keep coming back look further up line for the source.

 

[WC1]

Pretty sure they are not calcium.

 

[Paul Barnes]

I had the exact same issue after I moved into a home that the previous owner never cleaned the tank. I just scrubbed it out and I was shocked how much dirt/mildew came off. It’s clean now with none of that floating whittle sediment. Never had the issue again.

 

[WC1]

Is the white stuff a product of dezincification ?
It usually has a white fluffy appearance.