Impellers, especially the small ones for small tanks, even just 1 grain of nearly microscopic sand or a tiny piece of plant leaf, "anything", can put them out of line.
Take a brush, to the volute (the place the impeller rides) , and rinse the area.
I do this every time I clean the filter (do a water change) consider it a necessary part of normal maintenance.
The more the impeller rattles the more it will wear, and wobble and get worse, and can break the mechanism.
I know its hard to see, but a wobbly impeller wore a figure 8 in the housing of this 500gph pump.
below a piece of carbon got in a trashed a volute