It's weird, but I think they have more fun in the empty aquarium without
paper shreds or anything at all in it.  Last year when I had it out (for
playing in snow), they had a total ball with it just jumping in and out.
They get so vigorous in it that I was concerned that they were bonking
their heads against it too hard!  They get to wrestling so that it sounds
like a pair of sneakers in a dryer! :o)
 
Gary
[Posted in FML issue 4327]