Emme got a cup/plate set as a gift. I instinctively cut out the top and filed it away with my cardboard knowing it had some crafty potential. Well here is what we came up with. Lulu smeared, rolled and generally had a blast painting the cardboard side. I cut out fish and she placed them onto the wet paint and smeared and rolled some more. After it was dry I punched two holes and strung some yarn through the holes and hung it on a plastic suction cup hook on our big window.
This is an easy and fun craft to do with small children on up. Older children can add more details (paint the frame, add beads to the yarn hanger, add plant life...or forget the aquarium and turn it into a window and paint a scene outside.) Note: you can glue the fish down to ensure they wont peal up.