Generally a pump prop turns or doesn't turn. So that you're getting some water I assume the problem is elsewhere. Clogged line. Or air in the line which can act exactly like a clog.

Try the pump by itself in a bucket of clean water and see how well it works. If you still get a trickle at least you know it's the pump. I'd look at the prop for damage. Possible the shaft broke but still graps sometimes but pretty unlikely. Beyond that buying a new pump is the easiest fix. Most pumps of that size are sealed.

Check the shaft carefully for string or especially hair wrapped around it. It will probably need to be cut away with an exacto knife. I have short red hair but I have found both long blond and brunette hairs. Since we don't have any mermaids I assume the birds drop it in the water when collecting for nesting material.