Hi all, I have two of the same type of flexible aerators in two different freshwater tanks. However, one of them gets clogged up easily and visibly there is a white coating over it. The other however, does not have that white coat and doesn't get clogged up. When it gets clogged up, it causes my air pump to vibrate quite badly.

Could anyone advise me the reason or how can I prevent the aerator from clogging?