I think it would be cool if the fountain kept tract of the ammount of gralats you've thrown in.

1 or 2 visible gralats means you have donated < 10
5 through 10 visible gralats means you've donated about 100
20 or so visible gralats means you've donated about 500 gralats
If the bottom of the fountain was full of gralats it means you've donated 1000 gralats
And if there are more visible gralats than water, it means you've donated 2,500 or more gralats